18. 
19. 
21. 
Peis « 
126 
Vegetative axes densely corticated by intricately woven 
filaments ; main branches arising all round the stem, making 
a very dense and bushy plant ; secondary branches pinnate ; 
sporangia in groups hidden in the axils of branches 
Stypocaulon ...p. 
Thallus elongated and tubular = he 
Thallus rounded, irregularly lobed or sub-spheeeen 
Thallus forming a stalked “button” frequently hollow, from 
the centre of which spring forked thongs bearing conceptacles 
of oogonia and antheridia .... ane Himanthalia ...p 
Thallus at first solid, but soon becoming hollow, shewing two 
layers of tissue, the outer of which consists of radially arranged, 
monosiphonous assimilating threads ... Leathesia ...p 
Thallus hollow, of two layers of tissue, the outer of which is 
apparently parenchymatous ... ec Colpomenia ...p. 
Thallus branched only at the base, cylindrical, regularly con- 
stricted at intervals, tapering towards the apex, small cells 
on surface transformed into sporangia but not localised 
into definite sori ae Ee Scytosiphon ...p 
Thallus irregularly distended, aren wider towards the apex, 
dotted all over with sori of colourless hairs and sporangia 
Asperococcus. ...p. 
(See note 3, p. 105.) 
Thallus branched, branches either opposite or in whorls ; 
unilocular sporangia eae on the surface in whorls or 
in patches eee Se coe Siviaria ...P. 
Thallus at first solid, ieee uoitees ic of the axis increasing 
in size towards the periphery, but covered externally by a 
single layer of small cells; unilocular sporangia in external 
sori, accompanied by groups of club-shaped filaments forming 
minute dark-coloured warts over the surface Stilophova ...p. 
Small thalli forming globular or irregularly lobed gelatinous 
masses less than 24 inches in diameter. Surface layer of the 
plant formed of radially arranged assimilatory filaments 
Leathesia =.=: 
Thallus smooth, unbranched solid and whip-like, slippery 
to the touch, 1-6 feet or more in length. ae Chorda_ ...p. 
Thallus 3-10 inches long, branched, of extreme slipperiness ; 
with a core of more or less coherent colourless filaments of 
large cells and a cortical mantle of radially arranged, club- 
shaped, monosiphonous branches, more or less separable 
under pressure 
Thallus of other organisation 
Irregularly branched thallus, gelatinous, built up of central 
core of longitudinal rows of large colourless cells, not inter- 
woven by horizontal filaments she ..» “Castagnea, ~-.p: 
68 
20 
19 
74 
oe 
as 
“29 
39 
58 
71 
fs 
22 
23 
7° 
