Key for red seaweeds (part c)

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 blade formed parts and a round and long stipe relative to blade length 9

Thallus with flattened or blade formed parts, lacking or with a small round stipe 12

9

Small (to 3 cm) and often occurring in groups, blade irregularly lobed or dicochomuosly branched, rare Erythrodermis traillii

Thallus normally larger than 3 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 or axes 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 (may also have lobes or proliferations) 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 lobes or 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 Norway Fimbrifolium dichotomum

33

Thallus monostromatic or distromatic 34

Thallus always with more than two cell layers 36

34

Monostromatic blade, irregularly dichotomously divided often in wedge-shaped lobes, elongated polygonic cells, blade with elongated sori when fertile Nitophyllum punctatum

Blades rounded or irregularly lobed, small and rounded surface cells 35

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, Neopyropia, 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

Plain blade-formed 37

Blade appearing irregular or dichotomously divided, of with lobes 39

37

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

Dark red blade 38

38

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

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