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Thallus pinnately branched; long pod-like air-floats divided 
by septa; receptacles on narrow forked branches Halidvys ...p.74 
Thallus finely divided, usually narrow (thickness of string), 
frequently covered with spiny emergences; air-bladders 
small, not very distinct, arranged in chains distending the 
finer branches ... ae AGS ae ... ‘CystOser aa 
Thallus expanded into a membrane, a lamina or a ribbon; 
branched or unbranched ; with or without a stem-like portion 
Thallus cylindrical or slightly flattened, branched or unbranched, 
not exceeding a quarter inch in diameter Bee oan 
Thallus more than 15 inches long when mature 
Thallus less than 15 inches long when mature 
Thallus provided with a midrib 
Thallus without a midrib 
Thin membranous papery frond with conspicuous yellow 
midrib, and if reproducing, a bunch of tongue-like branches, 
3-8 inches long, arising from the stalk below the frond ... 
Alaria ...p. 
Thallus ribbon-like, much branched, with serrated margins and 
marked midrib; thallus covered with groups of mucilage hairs 
Fucus serratus ...p. 
Large leathery fronds without midrib ; stalk circular or slightly 
ovoid in section; no mucilage hairs on the lamina 
Laminaria ...p. 
Large leathery fronds with a stalk distinctly flattened into 
a strap 14-34 inches broad, sometimes with frilled lateral wings ; 
base irregularly bulbous covered with short tubercles ; 
mucilage hairs on lamina ... Nod .» Oaccorhiza ...p. 
Thallus undivided, lanceolate, often pointed at the apex 
Thallus dichotomously or otherwise divided 
Sori of unilocular and plurilocular sporangia (either or both) 
forming flecks or spots on the thallus; substance somewhat 
delicate im texture, ke ae ... Punciaria” -.-p- 
Plurilocular sporangia formed without much distention of 
surface cells over large areas of the thallus ; substance of the 
thallus tough ... ae tie as .. Phylhits <p: 
Thallus without midrib, more or less dichotomously divided, 
becoming markedly narrower towards the ends of the fronds, 
which are almost linear; sori of stalked plurilocular game- 
tangia scattered over the surface of the thallus Cuwtlevia ...p. 
Thallus dichotomously divided, either with a midrib or with 
fronds not conspicuously narrowed towards the apices 
74 
31 
39 
32 
35 
33 
34 
72 
fe 
71 
38 
