127 
Irregularly branched, gelatinous thallus built up of a central 
core of filaments of large cells interwoven by fine threads 
running in all directions ; an inner cortex of cells decreasing 
in size towards the periphery and giving rise to corticating 
assimilatory filaments arranged in groups Mesogloia ...p.70 
A smooth, cylindrical, branched thallus, about 4inchin diameter, 
built up of a central core of solid tissue, large and small cells 
packed together ; cortex of very small compact, assimilatory 
filaments not easily separable under pressure Chordaria ...p.70 
Reproductive organs (oogonia and antheridia) sunk in con- 
ceptacles relegated to tips of fronds or borne on special 
lateral branches (receptacles) ... ban . » (Pucacede)i 24 
Reproductive organs not as above, or plant without receptacles 27 
Lower part of thallus in form of stalked disc with long forked 
strap-shaped receptacles springing from its centre Lae 
Himanthalia ...p.74 
Thallus flat, ribbon-like, much divided ; air-bladders, if present, 
in the course of the frond ac Spe Bee ae sty 26 
Thallus cylindrical, more or less ce bcaae Sec ae ee a2 
Thallus with large oval air-bladders in the course of the main 
axes ; Ovoid receptacles on short lateral branches, arranged 
in groups ... ante 5 Na Ascophyllum ...p.74 
Thallus pinnately iraneneay tie pod-like air-floats divided 
by septa; receptacles on narrow forked branches : 
Hahidrys ...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 ... se ae ime ss. OYSLOSELYA ...p. 74 
Small plants, 2-6 inches long, without air-bladders, growing at 
high water mark; channelled thallus hanging from rock with 
convex surface outermost... wae See Pelvetia ...p.74 
Larger algae, with or without air-bladders, not channelled ; 
receptacles terminal on divisions of the thallus Fucus ...p.73 
Plant a stalked disc of about 1 inch diameter Himanthalia ...p.74 
Small plant, 2-6 inches long, without air-bladders, growing at 
high water mark; channelled thallus hanging from rock 
with convex surface outermost ae te Peluetia ...p.74 
Plants provided with definite air-floats ... es Sen me 2S 
Plants not provided with definite air-floats ae des ser 30 
Thallus flat, ribbon-like, much divided, air-floats in the course 
of the frond  ... oh - ae Mat Fucus _...p. 73 
Thallus cylindrical, more or less ee wise as deer 229 
. Thallus with large ovoid air-bladders in the course of the main 
axis ; ovoid receptacles on short lateral branches, arranged 
in groups bes eee wine G00 Ascophyllum ...p.74 
