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Class Phaeophyceae – key to the South Coast genera

1a. Thallus largely endophytic in bigger algae

Streblonema

1b. Thallus epilithic, epizoic or epiphytic, sometimes with an endophytic base

2

2a. Thallus prostrate or crustose, without free erect parts

3

2b. Thallus with free erect parts

6

3a. Thallus prostrate, not strongly adherent to substratum, elevated by multicellular rhizoids

Cutleria (Aglaozonia phase)

3b. Thallus crustose, strongly adherent to substratum, with or without rhizoids

4

4a. Unilocular sporangia borne laterally in clusters on free paraphyses

Zeacarpa

4b. Unilocular sporangia borne terminally , immersed in a solid layer of paraphyses

5

5a. Anatomy of upward-curving filaments with no distinct cortical zone, unilocular sporangia sessile or on single-celled pedicel

Ralfsia

5b. Distinct cortex of vertical filaments above upward-curving medullary filaments, unilocular sporangia on pedicles of 3-6 cells

Neoralfsia

6a. Erect thallus consisting of uniseriate filaments

7

6b. Erect thallus of more complex morphology and anatomy

15

7a. Thallus of pseudoparenchymatous basal cushion bearing loose erect filaments, erect filaments uniseriate but plurilocular sporangia divided longitudinally (multiseriate)

8

7b. Thallus entirely uniseriate filamentous)

10

8a. Plurilocular sporangia terminal or lateral, never intercalary

Elachista

8b. Plurilocular sporangia intercalary or terminal and intercalary on same thallus

9

9a. Thallus tiny (to 0.5mm tall), basal cushion of well-developed medulla, cortex of upright assimilatory filaments

Elachistiella

9b. Thalli to 2.5 mm tall, basal disc of branched radial filaments bearing erect assimilatory filaments that are simple or branched basally

10

10a. Sporangia intercalary, sometimes divided longitudinally

Bachelotia

10b. Sporangia terminal or lateral, never intercalary

11

11a. Chloroplasts one or a few per cell, ribbon-shaped

Ectocarpus

11b. Chloroplasts discoid or stellate, several per cell

12

12a. Chloroplasts stellate, thallus comprising creeping basal filaments bearing erect filaments

Asterocladon

12b. Chloroplasts discoid, numerous

13

13a. Lateral branches inserted at almost right angles, sporangia with relatively large loculi (10-15 µm diameter)

Acinetospora

13b. Lateral branches inserted at relatively acute angles, sporangia with relatively small loculi (ca 5 µm diameter or less)

14

14a. Erect filaments profusely branched, meristematic zones at bases of each lateral, sporangia above and below meristems

Hincksia

14b. Erect filaments sparsely branched (near bases), meristematic zones at bases of erect filaments, sporangia borne near bases of filaments below meristems

Feldmannia

15a. Thallus a more or less globose mass, solid or hollow

16

15b. Thallus of a different shape

18

16a. Thallus clearly pseudoparenchymatous in structure

Leathesia

16b. Thallus parenchymatous in structure

17

17a. Thallus hollow, thin-walled (ca 6-7 cell layers)

Colpomenia

17b. thallus solid, thick-walled (at least 10 cell layers)

Iyengaria

18a. Thallus tubular, unbranched, like hollow skin

Asperococcus

18b. Thallus of a different shape

19

19a. Thallus forming tangles or tangled cushions of terete to slightly flattened, branched axes

20

19b. Thallus of a different shape

22

20a. Thallus solid, medulla of large cells, cortex of small pigmented cells

Chnoospora (in part)

20b. Thallus hollow

21

21a. Thallus very flaccid, forming loose tangles on estuarine vegetation, assimilatory filaments present on surfaces of apical branches

Stilophora

21b. Thallus forming fairly compact cushions, no assimilatory filaments present

Rosenvingea

22a. Thallus solid, branched, terete, up to 1 mm diameter and to 50 cm tall, with conspicuous terminal tufts of assimilatory filaments

Carpomitra

22b. Thallus without terminal tufts of assimilatory filaments

23

23a. Thallus without distinctly flattened parts of blades

24

23b. Thallus with either flattened axes or blades

37

24a. Ultimate branches clearly polysiphonous

25

24b. Ultimate branches not polysiphonous

29

25a. Branching regular, either opposite or alternate

26

25b. Branching more irregular

28

26a. Branching regularly opposite, pinnate

Battersia

26b. Branching regularly alternate, distichous

27

27a. Plants to 30 cm tall, main axes terete, ca. 1 m diameter, with uncorticated determinate laterals3-4 mm long in feather-like tufts

Phloiocaulon

27b. Plants to 3 cm tall, main axis ca. 100 µm diameter, whole thallus feather-like

Halopteris (in part)

28a. Plants (local species) rarely longer than 2 cm, lateral branches originating from sub-apical segments

Sphacelaria

28b. Plants to 10 cm or longer, lateral branches originating from lenticular cells cut off from the apical cell

Halopteris (in part)

29a. Thalli with a soft central core and mantle of free assimilatory filaments

30

29b. Plants solid, without free assimilatory filaments

32

30a. Axes 4-6 mm in diameter, central core rather loose

Myriogloea

30b. Axes 2-4 mm in diameter, central core fairly firm

31

31a. Thallus profusely branched in three orders, branches of third order fairly short (a few to 20 mm)

Myriocladia

31b. Thallus sparsely branched, branches arising near base

Levringia

32a. Main axes up to 0.5 mm thick, with many unbranched laterals

Chordariopsis

32b. Main axes 1mm thick or thicker, laterals not plentiful or crowded

33

33a. Axes and laterals up to ca. 1 cm thick, with leathery skin, mucilaginous core

Splachnidium

33b. Axes between 1 and 5 mm thick

34

34a. Axes 1-2 mm thick, fairly lax

35

34b. Axes more than 2 mm thick, tough

36

35a. Thalli up to 8 cm tall, terete to compressed, holdfast rhizoidal, fertile portions not visible to naked eye

Chnoospora (in part)

35b. Thalli up to 50 cm tall, fibrous, terete, holdfast conical, fertile thalli with obvious swollen receptacles in apical portions

Cystophora

36a. Holdfast branched, rhizomatous, axes fairly lax, to 2-3 mm diameter

Brassicophycus

36b. Holdfast conical, axes stiff, main axes to 5 mm diameter

Bifurcariopsis

37a. Plants consisting of short, simple blades, lanceolate to strap-shaped

Petalonia

37b. Plants with more complex external differentiation

38

38a. Plants (sub) dichotomously branched, fan shaped and variously cleft, or funnel-shaped

39

38b. Plants of a different branching type

45

39a. Plants with a broad apical meristematic zone

40

39b. Meristem of a single large apical cell or small apical region

44

40a. Fronds funnel-shaped, up to 2 cm diameter, with distinct concentric lines and whitish calcified upper layer

Padina

40b. Fronds (sub) dichotomously branched or fan-shaped

41

41a. Fronds strap-shaped, 2-5 mm wide and to 30 cm long, repeatedly branched

Zonaria

41b. Fronds fan-shaped, erect or decumbent

42

42a. Plants erect, to 30 cm tall, fronds broad fan-shaped, cleft, often with bluish iridescence, hair cells forming distinct concentric bands

Stypopodium

42b. Fronds a few to 6 cm long, lobed, fan-shaped, erect or decumbent

43

43a. Fronds without hair tufts, medulla of four cell layers, cortex of single cell layer on each surface

Exallosorus

43b. Fronds with hair-tufts in concentric zones, medulla a single layer of large cells, cortex of 2-4 cell layers on each surface, upper cortical cells forming visible longitudinal lines

Lobophora

44a. Plans with prominent midrib

Dictyopteris

44b. Plants without midrib

Dictyota

45a. Plants with holdfast of branched haptera and single stipe bearing large flat blade, sori visible as pale slightly raised areas

Ecklonia

45b. Plants with discoid/conical holdfast bearing one to several branched upright axes with many blades, reproductive structures (receptacles) on specialised branches

46

46a. Thalli strongly compressed in almost all parts, primary laterals in alternate, distichous arrangement imparting a zig-zag appearance to thallus

Oerstedtia

46b. Plants with branched upright axes bearing many flat leaf-like blades, flotation vesicles present

47

47a. Axes cylindrical or triangular in section, leaves a few to about 7 cm long

Sargassum

47b. Axes flattened in cross-section, leaves strap-shaped and to 20 cm long

Anthophycus

Citing this publication:

Anderson RJ, Stegenga H, Bolton JJ. 2016. Seaweeds of the South African South Coast.
World Wide Web electronic publication, University of Cape Town, http://southafrseaweeds.uct.ac.za; Accessed on 18 December 2018