Algae1_all-split2_Page_008

13 - With radial striations and sometimes concentric
zones; usually quite free or only loosely attached
to the substratum; margin one cell thick ---- Zonaria (29)
13 - With no zones or striations; usually
adhering completely to the substratum or free
only at the multicellular margin ----- Ralfsia occidentalis
14 - Thallus with holes ----- Hydroclathrus clathratus
14 - Thallus without holes ----- Colpomenia sinuosa
15 - Branches lax, of different lengths and only one cell
broad ----------- Ectocarpus (30)
15 - Branches stiff, often unbranched in erect fascicles,
of uniform length and multicellular in cross -
section ---------- Sphacelaria (32)
16 Primary branches bearing proliferations between
successive leaved of secondary branches --- 18
16- Primary branches smooth other than for branches
and leaves ----- 17
17- Primary branches flattened to at least the
secondary branch or leaf; receptacles spiney, branches
sometimes angled; bladders on flatteneed petioles
common ---- Sargassum echinocarpum
17- Primary branches flattened only to the first or
compressed to the second or third secondary branch
or leaf; receptacles smooth finger-like; bladders on
round petioles, usually absent ---Sargassum obtusifolium