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Green seaweeds
Brown seaweeds
Red seaweeds






Terrestrial plants





How to use the key page 3


Photos green seaweeds page 11


Photos red seaweeds page 18, 26, 39


Photos brown seaweeds page 56

Glossary and

illustrations page 61

Kjersti Sjøtun University of Bergen

Department of Biological Sciences 2019


How to use the key

This key is meant to be an aid in identifying seaweeds which are relatively common on the coast of Norway. However, a total of nearly 500 taxa of marine macroalgae have been recorded from Norway, and this key only covers around 200 of these. A number of rare species and most small or microscopic species are not included here, and only a few crust forming red and brown algae are included.

The main division of the seaweeds is according to colour. Species of Division Chlorophyta (green seaweeds) have chlorophyll a and b and are green, species of Division Rhodophyta (red seaweeds) have chlorophyll a and some accessory pigments giving a red colour (phycoerythrin and phycocyanin), and species of Class Phaeophyceae (brown seaweeds) have chlorophyll a and c and some accessory pigments giving a brown colour (fucoxanthin). Thus, one can divide seaweeds into the three main groups according to colour. Sometimes this may still be difficult, since specimens can be bleached. In such cases one can look at the basal part of the specimens, where the original colour normally can be seen. You should also be aware of the fact that some red seaweeds can have a brownish-red colour. If you do not reach the correct species by using the brown seaweed key you may instead try the red seaweed key-

The key is based on grouping species according to specific characters, and some species may be intermediate and difficult to place in a group. These may appear more than one place in the key. You should also know that some species can have a very variable morphology, and that for some species young specimens may look different from adult specimens. Such variations are to some degree incorporated into the key.

For each of the three main groups the key is constructed so that the number on the left hand side normally gives two choices. Important information is often underlined. The red algae are initially divided in three main morphological groups, and one of these must first be selected. You proceed by following the chosen number on the right hand side. In order to see some characters a microscope is needed. If you make the right choices, you should arrive at last to the correct species or genus. For some genera systematic keys in the form of tables are made, where you have to compare your specimen with the information given in columns and rows. You should always check the name you have arrived at, by comparing the specimen to the description of the species in an illustrated algal flora. Many of the species are also illustrated by photos in this key, and nearly all photos are from the website http://seaweeds.uib.no

At the very back you will find a glossary, describing the special terms which are used in the key, and illustrations of different thalli types and forms of branching.

The key undergo continuous quality control by students from the UiB courses BIO309 and BIO311.

Kjersti Sjøtun


Some species are illustrated at pp 11-12

  1. Thallus up to 30-40 cm, thick, spongy and round axes,

    and normally dichotomously branched Codium fragile

    Thallus different 2

  2. Thallus leaf or blade-formed 3

    Thallus not leaf or blade-formed 7

  3. Thallus very small (<3-4 cm) and in high intertidal .

    often on resting places for sea birds, cells arranged in lines 4

    Thallus relatively big (several cm long) 5

  4. Thallus blade formed, <1 cm and narrowing to a short stipe, cells arranged in groups, most narrow separation lines between

    cells around 1/2 of widest ones Prasiola stipitata

    More rare and also terrestrial and also on other substrate than rock:

    • Thallus to 3-4 cm, often curly edge and lacking stipe Prasiola crispa

    • Thallus smaller and rounded, stipe short or absent, blade curled at edge, cells arranged in groups, most narrow separation lines between

      cells around 1/3 of widest ones… Prasiola furfuracea

  5. Long thallus with frilled and wavy edge, relatively narrow, tapering in

    both ends, older individuals partly hollow Ulva ('Enteromorpha') linza

    Thallus different and normally with an even or lobed edge 6

  6. Thallus distromatic, 1 pyrenoid per cell Ulva fenestrata

    (Ulva rigida probably under-reported, 2-4 pyrenoids per cell, margin with “teeth”)

    Thallus monostromatic, intertidal

    during spring and often appearing torn Monostroma grevillei

  7. Thallus hollow 8

    Thallus not hollow 9

  8. Key for tube formed taxa (Blidingia, Capsosiphon, some Ulva


    (‘Enteromorpha’)). Some important characters underlined.




    Cell arrangement

    Pyren- oids

    Capsosiphon fulvescens

    On rock in high intertidal, often in polluted sites

    To 20 cm, narrow, sometimes branched

    Characteristic pattern of 2 or 4 small cells (to 10- 12 μm) together in groups, separated by thick cell walls

    1 per cell

    Blidingia minima

    High intertidal

    To 10 cm long and 4 mm wide, often smaller.

    Several ind. from same attachm. disc.

    Small cells (5-10 μm), may be arranged in rows in the narrowest parts.

    1 per cell

    Blidingia marginata

    Brackish water

    Like B. minima, but more rare

    Small cells, always arranged in rows

    1 per cell

    Ulva linza

    Semi-exposed in rock pools or shallow

    Light green, flat with wavy edge, hollow margins

    Cells (15-20 μm) arranged in rows, rectangular with rounded corners

    Norm. 1 per cell

    U. intestinalis

    Most common Ulva, very common in rock pools

    Tubular and narrowing to the base. Can be compressed.

    Characteristic hood- shaped chloroplast, placed apically in cell. Cells 8-20 µm diam.

    1 per cell

    U. compressa

    Variable, but not in low salinity

    Variable, but much branched and often com- pressed

    Characteristic hood- shaped chloroplast, usually placed apically in cell. Cells 15-30 µm

    1 per cell

    U. prolifera

    Abundant at eutrophicated sites

    Very variable, may be branched or not

    Cells to 18 μm in longest direction and can be placed in long


    1 per cell centrally placed

    U. flexuosa


    Normally only first order branches

    Large cells (to 30 μm in longest direction) rectangular and arranged in rows


    per cell

    U. clathrata


    Highly blanched tubes

    Large cells (20-50 μm in longest direction), often in rows.

    Chloroplasts creating a lattice-like pattern

    Several per cell

    U. criniata

    Closely related to U. clathrata

    Highly branched, with some short thorn-like branches

    Large cells (20-50 μm in longest direction), often in rows.

    Chloroplasts creating a lattice-like pattern

    Several per cell

  9. Thallus branched 10

    Thallus not branched (or with few, short (1-4 celled) branches)… 16

  10. Thallus siphonous 11

    Thallus uniseriate 13

  11. Thallus siphonous with main axes, side branches more or

    less in one plane, normally no cell walls 12

    Thallus siphonous and small, irregularly branched, cell wall formes

    between main axis and side branch Derbesia marina

  12. Side branches not regularly in one plane Bryopsis hypnoides

    Branches regularly in one plane Bryopsis plumosa

  13. Thallus with short hook-formed branches and/or rhizoids (with little

pigment) growing downwards along axes at the base 14

Thallus lacks this, and side branches always initiated from top part of a cell 15

15 Key for marine (and marine-brackish) Lychaete and Cladophora. Some important characters underlined. Table continues on next page:



Branch system

Cell shape and size


Lychaete pygmaea

Diminutive; to 1.5 mm


Barrel-shaped, discoid holdfast


Cladophora rupestris

Stiff, broom- like tufts, dark green

Irregular, 1-4 laterals per cell

Main axes cell diam. 90-220

µm, length:width ratio 2-7. Thick cell wall

Intertidal, common

C. albida

Dense tufts with spongy texture

Main axes with branches of different age, often

bundles of flexed branches

Main axes cell diam. 20-90 µm,

l:w ratio 1.5-8.

Apical cell rounded tip

Intertidal, often in rock pools

C. dalmatica

Light pale to grass green.

Main axes ending in acropetal to irregular branching. Tips often bent (falcate)

Apical cell diam. 13-55 µm. Main axes cell diam. 60-150 µm, l:w

ratio 2-20. Cell walls thin, apical cell rounded tip

Marine-brackish, rock pools to shallow subtidal

C. flexuosa

Genetically close to C. sericea and

C. albida

C. hutchinsiae

Coarse tufts to 40 cm

Younger branches between older ones (sometimes branches slightly acropetal in tips)

Ap. cell diam. 90-195 µm.

Main axes cell diam. 200-400

µm, l:w ratio 1- 3.5

Littoral and upper sublittoral, rare in Norway

C. laetevirens

Spongy tufts

Branches often end with acropetal, sometimes flexed or falcate branching

Ap. cell diam. 35-110 µm.

Main axes cell diam. 100-260

µm, l:w ratio 2- 10

Littoral and upper sublittoral, rare in Norway

C. sericea

Light green, branching angle often


Younger branches between older ones

Main axes cell diam. 55-170

µm, l:w ratio 1-

15. Apical cell tapering

Marine to brackish, in the littoral zone

C. vadorum

Akinets may occur: cells short and thick walled

Branching with acropetal organization in attached individs

Main axes cell diam. 120-200,

l:w 2-11

Brackish localities

C. vagabunda

Light to dark green

Main axes ending in acropetal branching

Main axes cell diam. 80-300

µm, l:w ratio 1.5-15

Marine - brackish, often loose lying in sheltered bays

14 Big, dark green thallus, some short pointed or spinous branches,

grows in wave-exposed intertidal during spring Acrosiphonia arcta

Small, light green thallus, densly branched and with a spherical outline,

wave-exposed intertidal during spring Spongomorpha aeruginosa

  1. Thin entangled thalli, <100 µm in diameter, need

    microscope to see each individual. 17

    Macroscopic, uniseriate thallus, >200 µm in diameter 21


  2. Thallus with a few 1-4 celled branches Rhizoclonium riparium

    Thallus without a few short branches 18

  3. Thallus biseriate, sheltered in high intertidal Percursaria percursa

    Thallus uniseriate 19

  4. Forming a green felt-like cover on rock in spring 20

    Forms soft, light green ”bundles” of curly thalli

    entangled with other algae, cells 50-100 μm in diam Chaetomorpha ligustica

  5. Thallus with band-shaped, parietal chloroplast, in

    wave-exposed intertidal during spring Ulothrix sp.

    Thallus not with such chloroplast, cells slightly barrel-shaped,

    often in association with Ulothrix Urospora sp.

  6. Thallus dark green and with big cells (basal cell 1-3 mm long),

grows wave-exposed in shallow subtidal Chaetomorpha melagonium

Thallus bright green, dense vegetation in rock

pools during summer, or entangled in high intertidal,

cells 200-300 μm in diameter Chaetomorpha linum

(Chaetomorpha area)

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4f97dab3be20a.jpg http://seaweeds.uib.no/bilete/thumbnails/b600/Bryopsis%20hypnoides%20specimen%20from%20Espegrend%20Hordaland.jpg

Codium fragile subsp. fragile Bryopsis hypnoides


Chaetomorpha Chaetomorpha ligustica Rhizoclonium riparium melagonium

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4b94b4bd009ca.jpg image

Cladophora rupestris Ulva fenestrata Ulva linza

image http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4b97408f5fe56.jpg

Ulva intestinalis Cells with chloroplast and Blidingia minima

pyrenoid (arrows)

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4933971fc039f.jpg image

Monostroma grevillei Spongomorpha aeruginosa (enlarged)


Acrosiphonia arcta, habit Rhizoids Hook branches


Illustrations of some species follow after each category

Find the category that fits best for the specimen you want to identify:

Crusts or cover on rock, or rugged or loose-laying irregularly branched lumps of calcified algae go to page 17

Thallus upright with round (or rounded) axis or axes in cross section,

not flat in any part go to page 19

Thallus upright and flat or with some flat or flattened parts go to page 33

Crusts or cover on rock, or rugged or loose-laying irregularly branched lumps of calcified algae:

  1. Crusts or cover on rock or other substratum 2

    Loose-laying lumps of calcified algae,

    rugged or with stunted branches 7

  2. Thallus calcified (cells incrusted with calcium) 3

    Thallus crust-formed but not calcified 4

  3. This is a large group with many species which are difficult to identify. Two species are common and relatively easy to identify:

    Lithothamnion glaciale: pink, outgrowths like warts or with stunded branches. Grows in the subtidal as crusts on the rock or as loose-laying lumps (maerl).

    Phymatolithon lenormandii: mauvish, relatively smooth surface and normally with a conspicuous white growth zone along the edge. Common in the intertidal.

  4. Crusts or cover on rock mainly in the intertidal 5

    Crusts on rock and other substratum in the subtidal 6

  5. Thin and rusty red cover on rock Hildenbrandia rubra

    Up to 2 mm thick gelatinous and dark purple crusts in lower part of

    intertidal (sporophytic stage of Mastocarpus) 'Petrocelis cruenta'

  6. Can be several species, and normally fertile structures are needed for identification. A commonly occurring species is Cruoria pellita which can be identified by having zonate tetrasporangia

  7. Loose-laying irregularly branched lumps of calcified algae (maerl); several species, difficult to identify. Common species are:

Lithothamnion glaciale, L. corallinoides and Phymatolithon calcareum


Hildenbrandia rubra


Phymatolithon lenormandii


Zonate tetrasporangium

Cruoria pellita

Thallus with round (or rounded) axis or axes in cross section, not flat in any part:

  1. Thallus hard and calcified, erect, branched and articulated 2

    Thallus not calcified 3

  2. Oppositely branched, common in the littoral Corallina officinalis

    Dichotomously branched, relatively rare… Jania rubens

  3. Thallus hollow or partly hollow(often obscure in small/young ind.)

    or with cross walls (septa) at regular intervals 4

    Thallus not hollow 10

  4. Thallus small (up to 1 cm), mat-forming, dark red and with

    strong constrictions, special places in upper intertidal Catenella caespitosa

    Thallus bigger and not mat-forming in upper intertidal. 5

  5. Occurring only in intertidal and mainly with 1rst order branches… 6

    Mainly sublittoral and normally with more than

    1rst order branches (except young individuals) 7

  6. Short main axis and long side branches, spring/summer

    in the intertidal, bleached/yellow during summer Dumontia contorta

    All year around, very variable in morphology but

    relativly firm thallus, only in North Norway… Devaleraea ramentacea

  7. Thallus with opposite branches or branches set in whorls

    (may be obscure in young individuals) 8

    Thallus not with consistently opposite branches

    or branches set in whorls 9

  8. Axes with cross walls at regular intervals, which carry

    opposite or whorls of branches Chylocladia verticillata

    Axes with very strong constrictions, short side branches

    and limited to the intertidal of southwest Norway Lomentaria articulata

  9. Clearly hollow in all parts, branches can be in one plane

    or not, axes often with short branches between larger ones,

    branches with constrictions at the base Lomentaria clavellosa

    Axes hollow in lower parts, main axis with irregular and repeated branching,

    some branches gradually narrowing like tendrils Cystoclonium purpureum

    Thallus not hollow:

  10. Small, unbranched thalli 11

    Thallus with branches 12

  11. Thallus pluriseriate (except young thalli), brownish red,

    thin "hair", forming felt-like patches intertidally in wave-exposed

    sites during spring Bangia fuscopurpurea

    Uniseriate and normally microscopic, star formed

    plastid Erythrotrichia carnea

  12. Thallus uniseriate, but axes may partly be covered with

    rhizoidal cortex cells… 40

    Thallus pluriseriate but may have uniseriate short side

    branches with determined growth 13

  13. Thallus repeatedly dichotomously branched 14

    Thallus not dichotomously branched 18

  14. Thallus uniseriate with large cells, visible

    to the naked eye Griffithsia corallinoides

    Thallus pluriseriate 15

  15. Repeatedly dichotomously branched, thick axes (around 2 mm in diameter) 16

    Repeatedly pseudodichotomously branched, axes < 2 mm 30

    (E.g. some Vertebrata, Polysiphonia, Ceramium)

  16. Thallus dark red, soft, gelatinous, sparsely dichotomously

    branched, wave-exposed intertidal in summer Nemalion elminthoides

    Firm and cartilaginous axes… 17

  17. Basis as a round disc Polyides rotunda

    Basis as branched "roots" Furcellaria lumbricalis

  18. Thallus with numerous small uniseriate side branches in all parts of thallus 19

    Thallus not with numerous uniseriate side branches (or present only in apics) 22

  19. Axes divided in segments, which may be obscured by cortex in lower parts… 20

    Axes covered by cortex in all parts, sections normally

    not visible, present in Skagerrak… Dasya baillouviana

  20. Main axes with cortex in basal parts 21

    Axes without cortex, short uniseriate

    side branches set in a spiral Vertebrata byssoides

  21. Short uniseriate side branches, one per segment Dasysiphonia japonica

    Uniseriate side branches with a pluriseriate basal part, formed

    every 2-3 segments, branches in one plane Heterosiphonia plumosa

  22. Thallus with side branches in one plane 23

    Axes and side branches not in one plane 29

  23. Some type of consistent regular branching present in all or parts

    of thallus (alternate, opposite or unilateral) 24

    Branching not consistently regular in any part of thallus 27

  24. Narrow, flattend axes, main axis with more or less alternating side branches,

    last orders branches placed unilaterally (like a comb) Plocamium lyngbyanum

    Regular opposite or alternate branching present… 25

  25. Branching consistently alternating in all parts of thallus, axes divided

    in segments without cortex cells… Symphyocladiella parasitica

    Branching consistently opposite 26

  26. Side branches oppositely placed, often one shorter that the other in an alternating way (cystocarp replace short side

    branch in fertile individuals) Bonnemaisonia asparagoides

    Oppositely branched, one of the pair often shorter than the other

    in an alternating way, stiff and with a broad mid axis… Ptilota gunneri

  27. Bright red, main axes and side branches flattened, branches of

    1-2 (3) orders, placed opposite or irregular… Gelidium spinosum

    Often brownish red, more or less flattened, cartilaginous,

    branches stunted and placed irregularly 28

  28. Thallus with a round attachment disc Osmundea oederi

    Thallus with stolons (relatively rare)… Osmundea pinnatifida

  29. Thallus clearly segmented or striped, at least visible in young parts 30

    Thallus completely covered with cortex cells, axes do not

    appear segmented or striped 33

  30. Segments formed by cells of equal height (at least 4), can be covered by elongated cortex cells.

See key (several genera)… 31

Axes appear more or less striped. Thallus with large often round central cells, with a ”girdle” of cortex cells in the junction, or more or less covered by cortex, tip ending in two branches curled towards each other.

See key for Ceramium 32

  1. Occasional conspicuous hook-formed branches… Bonnemaisonia hamifera (n)

    Never with hook-formed branches… 34

  2. Thallus with clear main axes, and always attached 35

Thallus not with clear main axes, normally loose-laying 38

  1. Key for Polysiphonia, Melanothamnus, Savoiea, Leptosiphonia, Carradoriella and Vertebrata. Not included: P. hemisphaerica (rare southern species, recorded west to Lindesnes)


    No periaxial cells or arrangem. of plastids

    Cortex cells

    Thallus habit/ Branching


    Vertebrata byssoides



    Short uniseriate side branches set in a spiral


    Vertebrata lanosa



    Bushy thallus

    On Asco- phyllum

    Vertebrata fucoides


    Lacking or

    some near the base

    Several main axes, morphology varies

    Intertidal, subtidal

    Vertebrata nigra

    9-13 (spiral formed)


    Strongly branched, many short side shots set spirally

    Intertidal, subtidal

    Savoiea arctica



    To 10-15 cm, dark red, long segments in middle part

    North Norway, subtidal (deep)

    Carradoriella elongata


    With cortex almost to the apexes

    Relatively thick main axes with thinner end axes (reduced to main axes in autumn)


    Polysiphonia stricta



    Thin branches twisted round each other. Rhizoids with connection to periaxial cell

    Intertidal, subtidal

    Leptosiphonia fibrillosa


    Cortex at the base

    Soft, thin branches Rhizoids not connected to

    periaxial cell

    Intertidal, subtidal

    Leptosiphonia brodiei


    Main axes with cortex

    Bundles of short branches

    Intertidal, wave- exposed

    Melanothamnus harveyi


    Plastids placed innermost, towards the central cell

    Main axes covered with cortex at the base

    Main axes strongly branched to thinner side branches

    Upper subtidal, often epiphyte

  2. Key for Ceramium. Ceramium botryocarpum and C. siliquosum are not included (probably rare).


Cortical bands with spines

Cortex cell cover

No of periaxial cells

Habitat, branching

Ceramium shuttleworthianum

Yes, basal cell can be longitudinal divided

Confined to cortical bands


Small, wave- exposed intertidal, strongly inrolled apics

Ceramium deslongchampsii


Confined to cortical bands


Apics slightly incurved.

Tetraspor. naked. Rare

Ceramium sungminbooi


Cortical bands

sparse, only at nodes


Apics slightly incurved

Ceramium diaphanum


Strongly confined to cortical bands, often collar-like


Inrolled apics, open (>60°) branching

Ceramium “strictum” Name not valid


Confined to cortical bands


Occurs in relative brackish water (Skagerrak, Hardangerfjord).

Thin axes

Ceramium virgatum


Completely covered


Few adventitious branches, strongly irregular branching every (6)10-20(30)


Ceramium secundatum


Completely covered


Strongly inrolled apics,adventitious branches common, relatively regular branching every (8)10-15 node

Ceramium pallidum


Normally not complete


Inrolled apics, often epiphyte

  1. Short main axis with long 1rst order side branches,

    intertidal in spring Dumontia contorta

    Long main axes, branches of more than 1rst order… 36

  2. Cross section of axes shows a round central cell 37

    Not a round central cell, main axis with irregular and repeated branching,

    some branches gradually narrowing like tendrils Cystoclonium purpureum

  3. Main axes with side brances often in “bundles",

    but very variable in habit… Rhodomela confervoides

    Main axes densely set with short branches, often epiphytic

    on stipes of Laminaria hyperborea Rhodomela lycopodioides

  4. Not with clear main axes, Stiff and thin branches, almost black,

    often loose-laying but also growing attached in intertidal Ahnfeltia plicata

    Cartilaginous, somewhat flexible branches,

    diameter 1-2 mm 39

  5. Sparsely and irregularly branched, in warm bays… Gracilaria gracilis

    Like the former but more brownish in colour, introduced and

    spreading in Skagerrak… Gracilaria vermiculophylla

    Thallus uniseriate, but axes may partly be covered with rhizoidal cortex (note that this is a large group with many species which are difficult to identify):

  6. Thallus with irregular branching 41

    Thallus with a regular branching pattern 43

  7. Thallus with small pigmentless gland cells visible

    in "corners" between cells… Bonnemaisonia hamifera (2n)

    Thallus without gland cells… 42

  8. Plastids with large and conspicuous pyrenoids… Rhodothamniella floridula

    Without such pyrenoids and small thalli (< 1cm), several genera: Acrochaetium, Colaconema, Rhodochorton, Meiodiscus, Rubrointrusa

  9. Thallus with dichotomous branching and large cells

(visible by the naked eye)… Griffithsia corallinoides

Thallus with thin axes (relatively small cells) and regular branching:

Several genera, e.g. Callithamnion, Antithamnion, Aglaothamnion, Gaillona* Consult a special Ceramiales key

* Gaillona seposita: Characteristic alga in wave-exposed intertidal; small, brownish red, very densly branched and bushy

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4787706e351bb.jpg http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4a1678a5177b4.jpg

Corallina officinalis Jania rubens (strongly enlarged)


Catenella caespitosa (strongly enlarged)

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4b94b6be66766.jpg http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4724c6f65f81a.jpg

Dumontia contorta Chylocladia verticillata


Lomentaria clavellosa (can also have a flat form)


Bangia fuscopurpurea Microscop view of thalli

image image

Gelidium spinosum Osmundea oederi


Osmundera pinnatifida Stolon growth with new upright thalli


Ptilota gunneri


Bonnemaisonia asparagoides


Vertebrata byssoides


Heterosiphonia plumosa


Dasysiphonia japonica

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4bbc53498cd84.jpg http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4bbc591ee34d9.jpg

Ahnfeltia plicata Gracilaria gracilis

image http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4933ed2382d2e.jpg

Polyides rotunda Bonnemaisonia hamifera (epiphytic)

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno49f89b331ba2e.jpg image

Griffithisa coralliniodes Pterothamnion plumula Branch detail in

microscope, gland cells


Carradoriella elongata Detail in microscope


Vertebrata fucoides Detail in microscope


Ceramium schuttleworthianum Branch tips with spines on the outside (strongly enlarged) of the cortex bands

Thallus flat or with some flat or flattened parts:

  1. Flat part of thallus with conspicuous mid-rib extending to the apical end 2

    Thallus without such mid-rib 6

  2. Thallus alternating or pseudodichotomously

    branched, with narrow blade “rim” around mid-rib Membranoptera alata

    Thallus not branched in this way 3

  3. Thallus with lobes or proliferations from edge

    (which grow to new leaves), “oak leaf” like… Phycodrys rubens

    Thallus always with smooth edge 4

  4. Large, elongated blades, with conspicuous and

    macroscopic side nerves Delesseria sanguinea

    Relatively small blades lacking macroscopic side nerves,

    new blades grow from mid rib 5

  5. Microscopic side nerves like ”veins” formed by

    elongated cells in rows from mid rib Apoglossum ruscifolium

    No such clear microscopic veins… Hypoglossum hypoglossoides

  6. Thallus with nerves (polystromatic thickenings of blade) or veins

    but not forming a mid-rib to the apical end of thallus… 7

    Thallus lacking nerves or veins 8

  7. Several nerves proliferating the basal parts of

    a lobed blade, with additional veins… Cryptopleura ramosa

    Thallus with a stipe which continues as mid-rib some distance up on a

    lobed, otherwise monostromatic blade Haraldiophyllum bonnemaisonii

  8. Thallus with a round and long stipe relative to blade length (>1/4 of blade) 9

    Thallus with a relatively small stipe or lacking stipe 12

  9. Small (to 2 cm) and often occurring in groups, thallus with a conspicuous

    stipe, blade with irregular or lobed outline, rare Erythrodermis traillii

    Thallus normally larger than 2 cm and with relatively long stipe,

    and with dichotomously branched or lobed blades 10

  10. Flat part of thallus repeatedly (> 3 times) dichotomously divided,

    stipitate blades may branch off from stipe Phyllophora pseudoceranoïdes

    Flat part irregularly lobed or dichotomously divided to 3 times,

    new blades can grow from stipe or blades 11

  11. Basal stipe normally shorter than primary leaf, branching only in

    lower part, adventitious leaves without stipe Coccotylus truncatus

    Branching with stipitate leaves from all parts of plant,

    often apically. Coccotylus brodiei

  12. Thallus flat and with some kind of branching pattern 13

    Thallus is plain leaf or blade-formed or like a blade with lobes or splits 30

  13. Branches like proliferations or new blades growing from the

    edge of a relatively broad blade and in the same plane as the blade 14

    Not branching in this way… 16

  14. Thallus hollow, main axis like a broad flat blade narrowing to the top, first order side branches broad and with strong constrictions at the base,

    making them look like blades growing from the edge ……Lomentaria orcadensis

    Thallus not hollow… 15

  15. Blade can be divided in 2-3(4) lobed sections, and

    new blades grow from edge of the old blade Palmaria palmata

    Thallus more or less dichotomously divided, numerous thin

    proliferations from edge, North Norway… Fimbrifolium dichotomum

  16. Regular feather branching with opposite branches, one of the pair often shorter than the other in an alternating way, stiff and with a broad

    rounded mid axis… Ptilota gunneri

    Not consistent opposite branching 17

  17. Consistent alternate or unilateral branching in last orders of branching 18

    Irregular or dichotomous branching 19

  18. Main axes with inconspicuous mid rib and alternately branched,

    side branches end in 2-3 small "teeth" Odonthalia dentata

    Main axis with alternating side branches, where those of the last order

    are placed unilaterally (like a comb)… Plocamium lyngbyanum

  19. Irregular branching 20

    Dichotomous branching 26

  20. Thallus with a clear main axis 21

    Thallus without a clear main axis 25

  21. Thallus hollow 22

    Thallus not hollow… 23

  22. Main axes relatively narrow, side branches with constrictions at base,

    side branches can be in one plane or not… Lomentaria clavellosa

    Main axis like a broad flat blade narrowing to the top,

    first order side branches broad and with strong constrictions at the base,

    making them look like blades growing from the edge ……Lomentaria orcadensis

  23. Bright red, main axes and side branches flattened, branches of

    1-2 (3) orders, placed opposite or irregular… Gelidium spinosum

    Often brownish red, more or less flattened, cartilaginous,

    branches stunted and placed irregularly 24

  24. Thallus with a round attachment disc Osmundea oederi

    Thallus with stolons (relatively rare)… Osmundea pinnatifida

  25. Relatively big (up to 10-15 cm) and strongly dividedin wide branches

    or lobes, with a frilled edge when fertile Metacallophyllis laciniata

    Relatively small (up to 5 cm), strongly divided in many

    narrow branches, often on hapteron of kelp… Euthora cristata

  26. Dichotomous branching, some species also with new blades or

    prolifierations from edge of blades, in the same plane as the blade 27

    Dichotomous branching, thallus not with new blades or

    proliferations from blade edge 28

  27. Blades elongated and more or less dichotomously divided, numerous

    thin proliferations from edge, North Norway… Fimbrifolium dichotomum

    Short stipe, long ”crispy” elongated blades with parallel sides and

    divided in 2 or 3 lobes, with new blades growing from the to Phyllophora crispa

  28. Short stipe (may lack), small, thin thallus irregularly

    dichotomously divided, sheltered bays. Rhodophyllis divaricata

    Bushy in upper part, thallus narrowing to basal parts,

    occurring mainly in intertidal 29

  29. When fertile with small papilla or “warts” in upper part Mastocarpus stellatus

    Without papilla on blades, may iridize in sun Chondrus crispus

    Thallus is plain leaf or blade-formed or with lobes:

  30. New blades or prolifierations from edge of blade, in the same plane

    as the blade 31

    Thallus flat or blade-formed without proliferations 33

  31. New blades growing only from top of old blades. Short stipe, long ”crispy” elongated blades with parallel sides and divided in 2 or 3

    lobes often carrying new blades… Phyllophora crispa

    New blades or proliferations from edge of all parts of the blade 32

  32. Blade can be divided in 2-3(4) lobed sections, and

    new blades grow from edge of the old blade Palmaria palmata

    Thallus deeply lobed or more or less dichotomously divided,

    numerous thin proliferations from edge, North Norw Fimbrifolium dichotomum

  33. Thallus flat and without clear lobes or insertions (but may appear torn) 34

    Thallus with lobes or insertions 38

  34. Thallus monostromatic or distromatic… 35

    Thallus always with more than two cell layers 36

  35. Monostromatic leaves to 4 cm, small, rounded cells (3-8 um),

    sublittoral and always several individuals together… Porphyropsis coccinea

    Thallus normally >4 cm, vegetative cells grouped 2 or 4 together… Porphyra*,

    Pyropia, Wildemania

    Eight species recorded in Norway. Two intertidal species* are common and easy to identify: P. umbilicalis (with attachment point on the lamina) and P. linearis (short stipe and long and narrow lamina)

  36. Bright red or bleached small blade, round medulla cells Palmaria palmata

    Dark red blade 37

  37. Dark red blades, to 40 cm, often several from the same

    attachment disc. Medulla consists of elongated filaments Dilsea carnosa

    Dark red and rounded blades, to around 10 cm,

    North Norway. A short stipe from a notch in the blade Turnerella pennyi

  38. Monostromatic irregularly lobed blade,

    with scattered elongated sori when fertile… Nitophyllum punctatum

    Always with polystromatic blade 39

  39. Short stipe (may lack), thallus up to 2-3 cm, thin and

    irregularly dichotomously divided Rhodophyllis divaricata

    Thallus with lobes or insertions but not

    consistently dichotomously divided 40

  40. Thallus relatively big and divided in or lobes 42

    Thallus relatively small and divided in lobes… 41

  41. Small (to 2 cm) and often occurring in groups, thallus with a conspicuous

    stipe, blade with irregular or lobed outline, rare Erythrodermis traillii

    Relatively small (up to 5 cm), strongly divided in many

    narrow branches or lobes, often on hapteron of kelp… Euthora cristata

  42. Relatively big (up to 10-15 cm) and strongly divided

in wide lobes, with a frilled edge when fertile Metacallophyllis laciniata

Elongated blade divided in long lobes apically, rare… Halarachnion ligulatum

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno451cd64aeeb0f.jpg http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4bbc602bb6117.jpg

Membranoptera alata, tip of Phycodrys rubens

branch strongly enlarged

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno467bc9446a455.jpg http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno533920e85c446.jpg

Delesseria sanguinea Apoglossum ruscifolium


Hypoglossum hypoglossoides Detail showing blade structure

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4b964517136c3.jpg http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno5297006ee9358.jpg

Porphyra umbilicalis Porphyra linearis

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno533d3e2d1082e.jpg http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno48da18939c5ae.jpg

Dilsea carnosa Palmaria palmata

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno467bc4f9d6a67.jpg http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno467bc6bc32c20.jpg

Metacallophyllis laciniata Euthora cristata


Rhodophyllis divaricata


Chondrus crispus Mastocarpus stallatus


Phyllophora crispa


Plocamium lyngbyanum Detail showing branching


Some species are illustrated pp 56-59

  1. Thallus forms crusts on rock or other substratum 2

    Thallus different 3

  2. This group includes several genera, and species are difficult to identify. Two species are relatively easy to identify:

    Ralfsia verrucosa: brown crusts with a rounded outline and light edge, common in rock pools.

    "Aglaozonia": relatively loosly attached to the substratum, rounded lobes at the edge. The sporophytic stage of Cutleria multifida

  3. Thallus either like a button (flat disc) or with an irregularly spherical outline 4

    Thallus different 6

  4. Vegetative thallus like a button (flat disc), intertidal, long dichotomously

    divided receptacles when fertile… Himanthalia elongata

    Thallus with a irregularly spherical outline 5

  5. Thallus becomes hollow, parenchymatic tissue,

    surface covered with small cortex cells Colpomenia peregrina

    Thallus with pseudoparenchymatic tissue (rows of cells

    sliding away from each other under pressure), surface covered

    with 2-5 celled paraphyses Leathesia marina

  6. Erect part of thallus like unbranched and compact axis, sometimes

    with hairs (which may be pigmented) or very short side branches… 7

    Thallus different… 12

  7. Thallus small (<10 cm) and epiphytic 8

    Thallus large (> 20 cm and up to > 1 m)… 11

  8. Erect part of thallus like uniseriate small (max 2 cm) axes, growing

    together in brush-like tufts epiphytically on Fucus Elachista fucicola

    Mature thallus pluriseriate, several individuals

    growing together in tufts… 9

  9. Thallus covered with short side branches and hairs…….Myriotrichia clavaeformis

    Thallus not with short side branches 10

  10. Thallus pluriseriate and with hairs Litosiphon laminariae

    Thallus pluriseriate and lacking hairs Pogotrichum filiforme

  11. Long thallus > 1 m in summer, colourless hairs,

    Hollow in older individuals… Chorda filum

    Short pigmented assimilation hairs starting some distance

    from the base, only in spring in South Norway. Halosiphon tomentosus

  12. Thallus hollow 13

    Thallus not hollow (or only in part of axes in old individuals)… 17

  13. Branched from main axes (often oppositely branched)… Striaria attenuata

    Thallus not branched 14

  14. Intertidal, mature individuals with regular constrictions, several thalli originating from a common attachment point, spring

    (small individuals may appear compact) Scytosiphon lomentaria

    Mature thallus hollow and inflated but not with regular constrictions… 15

  15. Thallus hollow but dorsiventrally flattened,

    to around 40 cm long Asperococcus ensiformis

    Thallus not dorsiventrally flattened 16

  16. Thallus elongated and up to 30 cm long,

    inflated and bulbous, summer… Asperococcus bullosus

    Smaller, thalli like narrow tubes, often epiphytic Asperocuccus fistulosus

  17. Thallus flat and branched or with a blade-formed part 18

    Thallus with round or rounded axis in cross section and branched 43

  18. Thallus with flat or flattened branches 20

Thallus like a blade or carrying a blade-formed part

which may be divided (like fingers on a hand) on a stipe 32

  1. Thallus lacking a midrib 21

    Thallus with a midrib (may be difficult to see in some)… 25

  2. Thallus not dichotomously branched 22

    Thallus dichotomously branched, but may have

    additional side branches 23

  3. Thallus flat and oppositely branched, side branches

    narrowing towards base Desmarestia ligulata

    Thallus irregularly divided in narrow parts, each

    ending in a small hair tuft Cutleria multifida

  4. Thallus dichotomously branched and with additional side branches,

    axes flat and strap-like with relatively large gas vesicles… Ascophyllum nodosum

    Thallus dichotomously branched only 24

  5. With half-piped formed branches, growing in uppermost

    part of the intertidal, sheltered Pelvetia canaliculata

    Thallus with thin, flat branches, growing submerged Dictyota dichotoma

  6. Thallus with round gas vesicles Fucus vesiculosus

    Thallus without such round gas vesicles 26

  7. Thallus with a notched (serrated) edge Fucus serratus

    Thallus with a smooth edge 27

  8. Brackish species, often in river outlets, thallus relatively thin and flexible and often with inflated areas, and often the same individual can have

    varying width of branches. Fucus ceranoides

    Stiffer thallus, not growing exclusively in brackish sites 28

  9. Thallus with an indistinct mid-rib 29

    Thallus with a clearly visible midrib 31

  10. Thallus small (often < 5 cm), irregularly branched and flattened, growing in turf at a high level in the intertidal

    at special localities, rare Fucus cottonii

    Thallus always attached to rock in intertidal

    and with numerous caecostomata 30

  11. Thallus to 10 cm, growing only in strongly wave-

    exposed intertidal, long swollen receptacles Fucus distichus

    Larger thallus, often growing in harbour areas,

    long and swollen receptacles… Fucus distichus subsp. evanescens

  12. Thallus stiff and flat, elongated receptacles,

    dioecious, semi-exposed Fucus vesiculosus f. linearis

    Thallus often twisted, during summer with round receptacles

    hermaphroditic, upper intertidal, sheltered Fucus spiralis

  13. Thallus big and having a conspicuous stipe and blade, the blade

    can be plain flat, divided like fingers on a hand or have a mid-rib 33

    Thallus smaller (< 20 cm) and with a small stipe 39

  14. Lamina divided in broad parts, like fingers on a hand 34

    Lamina not divided 36

  15. Thallus with a round (or rounded) stipe, attached by branched hapteron 35

    Lamina with hair groups, thallus with a broad, flat, twisted or frilled stipe

    and unbranced, knobby (in large individuals) holdfast…….Saccorhiza polyschides

  16. Thallus with stiff and long stipe, subtidally

    and wave-exposed Laminaria hyperborea

    Thallus with a flexible stipe, forming a zone in the upper

    subtidal, wave-exposed Laminaria digitata

  17. Long and narrow lamina with mid rib Alaria esculenta

    Lamina without conspicuous mid rib 37

  18. Lamina with very frilled or wavy edge and

    often undulated middle parts Saccharina latissima

    Lamina plain and flat without frills or undulations… 38

  19. Plain lamina with hair groups, North Norway only…………Saccorhiza dermatodea

    Big and non-sectioned flat lamina: forms of Laminaria hyperborea and L. digitata

    which develop at sites with little water movement from waves and currents

  20. Attached by a small disc 40

    Attached by a small hapteron juv. Laminaria sp.or Saccharina latissima

  21. A small “ring” at the bottom of the stipe, hair

    groups on lamina juvenile Saccorhiza polyschides

    Not a small “ring” at the bottom of the stipe 41

  22. Thallus leaf-formed and narrow, growing in bundles, cross section shows small cortex cells and elongated inner cells,

    intertidal and wave-exposed 42

    Thallus leaf-formed and narrow, cross section shows cells

    with more or less same size and form Punctaria*

    * Punctaria plantaginea common during spring, blade 4-6 cells in cross section

  23. Blade >2 mm and up to 5 cm wide, growing in small bundles

    intertidally during spring, wave-exposed Petalonia fascia

    Blade very narrow (< 2 mm), growing in small bundles

    intertidally during spring, wave-exposed Planosiphon zosterifolius

    Thallus branched and with round or rounded axis in cross section:

  24. Thallus fully or mainly uniseriate 44

    Tallus pluriseriate in all parts (except apical cells or short side branches) 56

  25. Erect part of thallus unbranched, brush-like tufts

    epiphytically on Fucus Elachista fucicola

    Thallus branched in all parts 45

  26. Thallus pluriseriate in basal parts or with some cells longitudinally divided 46

    Thallus uniseriate in all parts 50

  27. Thallus with mainly opposite branching from main axes. 47

    Thallus not oppositely branched, or only a few times… 48

  28. Thallus pluriseriate in basal parts, oppositely branched or branches in whorls, or with unilocular sporangium opposite of branch,

    often epiphyte on Cladophora rupestris Isthmoplea sphaerophora

    Thallus may be pluriseriate in basal parts, is mainly oppositely branched from main axes, with conspicuous reproducing

    cells (1-2) placed intercalary in side branches Tilopteris mertensii

  29. Thallus may have round monosporangia with a dark

    brown content, normally on short branches Haplospora globosa

    Thallus with intercalary sporangia and gametangia, forming cell rows 49

  30. Intercalary sporangia or gametangia, disc-formed chloroplasts, may have some opposite branches and

    some cells longitudinally divided Pylaiella littoralis

    Loose-lying, short side branches and

    terminal sporangia common, rare Pylaiella varia

  31. Intercalary sporangia or gametangia, forming cell rows,

    disc-formed chloroplasts… 51

    Sporangia and gametangia as side branches, more or

    less cone-shaped 52

  32. Intercalary sporangia (unilocular or plurilocular), disc-formed chloroplasts, may have some opposite branches and

    some cells longitudinally divided Pylaiella littoralis

    Loose-lying, short side branches and

    terminal sporangia common, rare… Pylaiella varia

  33. Densely twisted axes (“dreadlocks”) and with small hook-formed

    side branches, often epiphyte on Fucus Spongonema tomentosum

    Not with small hook-formed side branches. 53

  34. Strongly elongated plurilocular sporangia often

    with a short stalk, chloroplast ribbon-shaped 54

    Stunted sporangia without stalk, often in series, disc-shaped chloroplasts… 55

  35. Brances in bundles especially in upper part, plurilocular sporangia often in rows adaxally on branches,

    not ending in a pseudohair Ectocarpus fasciculatus

    Plurilocular sporangia elongated and often

    terminating in a long pseudohair Ectocarpus siliculosus

  36. Key for the genus Hincksia :






    H. hincksiae

    To 10 cm

    Branches often to one side in upper part

    Adaxially in series, so dense that the sides meet

    Often epiphyte on Sacchoriza polyschides

    H. sandriana

    To 10 cm

    Branches in series to one side

    Adaxially in series, not so dense that the sides meet

    May also have unilocular sporangia

    H. granulosa

    To 15 cm

    Branching often opposite

    Sporangia round or rounded, often somewhat curved

    H. ovata

    To 4 cm

    Opposite or sparsely

    Sporangia often on a one-celled stalk

  37. Below top cells the axes are pluriseriate, and clearly divided in segments of cells with longitudinal divisions (seen in microscope, young shots).

    Axes may be covered with rhizoidal cortex 57

    Axes not clearly divided in segments in any parts… 58

  38. Key for Sphacelariales in Norway (continues on next page):



    Rhizoidal cortex

    Cross div. of cells in segments

    Propagule and zoidangia

    Dimen- tions


    Cladostephus spongiosus

    Short whorl-

    brances, set densely

    Yes, main axes



    Thal. to 10 cm

    Loose-laying or

    attached in intertidal

    Halopteris scoparia

    Alternating from main axes, last order branch

    very pointy




    To 4-5

    cm (in Norw.)

    Attached form rare, loose- laying form in sheltered bays

    Sphacelaria plumula

    Feather branching




    w. 3 short horns


    To 2 cm

    S. cirrosa

    From main axes




    w. 3 horns and 1 hair

    To 3cm, axes

    to 100 μ wide

    Often epiphytic (mainly Halidrys siliquosa)

    S. rigidula

    Irregular, thalli in small bushes



    Propagule with 2-4 horns. Uni- locular zoidangia on a curved


    To some cm

    Stolon growth. Branches of propagule not constricted at base

    S. triluboides

    Absent or sparsely




    w. 2 short horns

    Erect axes to 55

    μ wide

    Solitary hairs frequent, rare

    Chaetopteris plumosa

    Apical feather branching

    Yes, from cell of sec. segment in all




    To 10 cm

    Basal parts dark and coarsely branched.


    Battersia plumigera

    Apical feather branching

    Yes, from cells in the same

    plane as side br.


    Presence in Norway uncertain

    B. arctica

    Irregularly feather br.

    Main axes, sparsely


    Rare in Norway

    B. racemosa

    Irregular, sparsely



    Zoidangia in groups

    To 2cm, axes to 55

    μ wide

    No propagule, grows in sandy

    rock pools

    Sphacelo- derma caespitulum




    Pluriloc on 3-5 celled stalk

    To 1 cm,

    axes to 35 μ wide

    No propagule. Small erectt axes from a thick basal crust

    Sphacelorbus nanus




    Unilocular on a short stalk,

    < 1 cm, filaments to 23 (30)

    Rare in Norway, no propagule.

    Stolon growth,

    pluriloc on

    separate plants

    μ wide

    forms mats






    To 2cm,

    No propagule,

    teris radicans






    stolon growth,

    forms dense

    pluriloc on

    to 60 μ





  39. Thallus with gas vesicles (round or elongated like

    pea pods and ending in a narrow tip) on short stalks 59

    Thallus without gas vesicles (or with very few)… 60

  40. Thallus with small leaves and small, round gas vesicles Sargassum muticum

    Gas vesicles are elongated with compartments

    ("pea pods"), main axes are flattened Halidrys siliquosa

  41. Thallus with a consistent or nearly consistent regular branching pattern 61

    Thallus with irregular branching 63

  42. With long, dichotomously branched receptacles attached to

    a button-formed vegetative part. Himanthalia elongata

    With opposite or whorl branching 62

  43. Consistently oppositely branched Desmarestia viridis

    Commonly with opposite or whorl branches, hollow

    in most parts… Striaria attenuata

  44. Surface covered with paraphyses (seen in microscope)… 64

    Surface with angular cortex cells… 68

  45. Thallus slimy and gelatinous 65

    Tallus different 67

  46. Thallus to 5 cm, short branches and epiphytic on Zostera…. Cladosiphon zosterae

    Thallus larger and with relatively long branches… 66

  47. Thallus with relatively long 1st order branches and short

    2nd order branches, branches of equal thickness Eudesme virescens

    Thallus with branches of unequal thickness,

    paraphyses with barrel shaped cells at basis Mesogloia vermiculata

  48. Alternately branched from one main axis, almost only branches of 1rst order, thallus not hollow, low intertidal

    during summer. Chordaria flagelliformis

    Long 1rst order branches and short 2nd order branches ending

    in a hair, axes hollow in lower parts, unilocular sporangia… Acrothrix gracilis

  49. Fertile structures in conspicuous sori on surface of axes,

    consisting of sporangia, paraphyses and hairs 69

    Thallus not with such sori 70

  50. Pale yellowish, uneven and knotty surface with darker spots (sori), loose-laying in sheltered areas during summer, irregularly

    branched and axes with one central cell row Spermatochnus paradoxus

    Similar to S. paradoxus, but with 4-5 central cell rows,

    growing epiphytically on Fucus during summer… Stilophora tenella

  51. Thallus irregularely branched, with flattened axes (2-3 mm thick), laying loose

    in intertidal in sheltered bays Ascophyllum nodosum f. scorpioides

    Thallus with thinner axes and sublittoral… 71

  52. Irregular branching, dark and coarse branches set with small “spikes” during winter, new growth in spring seen

    as light brown shoots set with small bundles of hairs Desmarestia aculeata

    Thallus not with small “spikes” 72

  53. Growing shoots ending in a hair, axes with rectangular

    cortex cells covering large inner cells (microscope)… 73

    Growing shoots not ending in a hair, rounded cortex cells,

    often epiphytic on Chordaria flagelliformis Dictyosiphon foeniculaceus

  54. Rectangular cortex cells covering elongated

inner cells (not always easy to see) Stictyosiphon tortilis

Rectangular cortex cells covering large, round inner

cells (easy to see), small branches often uniseriate Stictyosiphon soriferus


Cutleria multifida, gametophyte sporophyte

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4c98b3a1465b8.jpg http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno48ac24d42d060.jpg

Dictyota dichotoma Laminaria digitata

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4b87c23fc5a01.jpg image

Ralfsia verrucosa Saccharina Alaria esculenta


http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno49d1c1397df79.jpg http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4b97429ce92b2.jpg

Ascophyllum nodosum Fucus spiralis

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4bd169430fcb2.jpg http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4b976d720f545.jpg

Fucus vesiculosus Fucus serratus

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4b964abfa68aa.jpg image

Fucus distichus Pelvetia canaliculata

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno466e536dbf8fc.jpg http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4d8f15e9cb8a7.jpg http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno52fcb32bba689.jpg

Himanthalia elongata Halidrys siliquosa Sargassum muticum


Desmarestia aculeata Desmarestia viridis Desmarestia ligulata


Chordaria flagelliformis Stictyosiphon tortilis


Elachista fucicola Mesogloia vermiculata


Isthmoplea sphaerophora

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno4843261b2ec5d.jpg http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno474c9a5d98efb.jpg

Cladostephus spongiosus Colpomenia peregrina


Petalonia fascia Planosiphon zosterifolius Scytosiphon lomentaria


Acropetal branching - Branches successively older (and longer) from top to lower part Adaxial - Placed on the up-side of branch, towards the main axis Adventitious branching - Branching occurring in an irregular manner, in addition to

regular branching pattern

Apical - Most distant part

Biseriate - Two parallel cell rows

Caecostomata - Small cavity under the surface, characteristic for a group of Fucus

Calcified - Cells with calcified cell wall (calcite), giving a hard, opaque structure

Central cell - Axial cell row in some groups

Chloroplast - Cell organell containing the pigments (act. referring to green plastids)

Cortex - Cells covering axes, can be small and round or elongated cells Cystocarp - Round or urn shaped female reproductive structure in some red algae Dichotomously branched - Y branched (see illustration)

Dioecious - Male and female gametes produced in separate individuals

Distromatic - Two cell layers

Dorsiventrally flattened - Flattened and with two distinct surfaces

Epiphyte - Grows on other algae

Feather branching- Branching is regular in a consistent way, side branches forming an “edge” like the one of a feather (see drawing)

Gamete - Sexual reproduction cell Gland cells - Small cells without pigment Hapteron - Root-like holdfast of seaweeds

Hermaphroditic - With male and female gametes in the same receptacle

Intercalary - Between cells, not in the apical part

Lamina - Blade-formed part of algae, normally referring to brown or red algae

Mid rib/mid nerve - A conspicious thickened part of thallus which can be followed along the thallus

Monostromatic - One cell layer

Nerve - Polystromatic thickening of blade

Node - Joint in a segmented axis (e.g. cortex band in Ceramium) Paraphyse - Small cell rows often associated with fertile structures in brown algae Parenchyma - Solid tissue, where each cell do not follow a fixed division pattern but

can in principle divide in 2 or 3 planes

Parietal - Located at the wall

Periaxial cells - Cells formed in a circle around the central (axial) cell

Plurilocular sporangium - Specialized branch or cell, divided in many rooms (loci), which each contain one spore

Pluriseriate - A cross section of thallus show more than one cell

Polystromatic - Several cell layers

Proliferation - Adventitious branching or outgrowths of new thallus part from an old one

Propagule - Vegetative reproduction unit, in Sphacelariales a specialized short branch ending in two to four “horns” (short branches) set perpendicular from the top of the branch

Pseudoparenchyma - Often (not always) loosely connected tissue, consisting of cell rows where cell can only divide in one plane

Pyrenoid - Round structure associated to chloroplast

Receptacele - Specialized part of thallus which produces gamets in some brown eaweeds (Fucales)

Rhizoid - Branch-like with little pigments and clearly different from the other branches, can attach thallus to the substratum

Segment - Thallus axes divided in conspicious sections consisting of one or several cells of equal height (in Sphacelariales some of these can divide within the section). The sections can be covered with cortex cells (see illustrations p. 65)

Siphonous - Thallus lacks cell walls or has only some cell walls, thallus is composed of one or more large cells with many nuclei

Stipe - Stalk-formed part of red or brown algae

Stipitate - With stipe

Thallus - The “body” of a multicellular alga or fungus (equals "plant" in embryophyta)

Unilateral - On one side only

Unilocular sporangium - Specialized branch or cell, with one room (loci), which contains many spores (asexual reproduction cells)

Uniseriate - Thallus composed of a cell row (may be branched or unbranched)

Veine - Cells forming a line pattern in the surface of the blade

Zoidangia - Specialized cells or structures producing flagellated reproductive cells

Different types of branching and thallus habits:





Regular branching patterns:

image image image image

Alternately branched Oppositely branched Whorl branched Opposite Alternate MA: main axis feather branched (br. in one

1: Branches of 1rst order plane, forming a feather outline)

2: Branches of 2nd order

Irregular branching:

image image image

Irregular from Irregular, no Irregular from main axis in one plane, main axis in all planes clear main axes but not like a feather

image image image

Dichotomously Flat/leaf-formed, Flat/leaf-formed, Flat/leaf-formed,dichomo- divided/branched dichotomously divided/ dichotomously divided/ mously divided/branched

branched branched with stipe with mid rib

image image


Plain leaf-formed/ Flat/leaf-formed and with Leaf-formed, with

spherical outline (if round) lobes/sections/insertions mid rib/nerve and side nerves

Thallus pluriseriate, and

Segmented Striped


Thallus uniseriate:

Segmented thallus with elongated cortex cells:

http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno52d9376b2016d.jpg http://seaweeds.uib.no/bilete/thumbnails/b600/seaweedsuibno479dc0e54b1e6.jpg




Latest published photos

Gelidium pusillum
Sampling date 2014-10-08
Published 2020-07-06


Fucus spiralis
Sampling date 2017-08-08
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Sampling date 2020-06-17
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Pyropia leucosticta
Sampling date 2008-06-01
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Pyropia leucosticta
Sampling date 2008-06-01
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