Io. 
IDES 
124 
Thallus in form of horizontal crust of parenchymatous organisa- 
tion, attached to the substratum by rhizoids; central cells 
large, surface cells small and regular. (These surface cells 
are not to be confused with the closely packed terminal cells of 
upright filaments which are not present in this plant) 
Aglaozonia ...p.73 
Filaments monosiphonous ... ae 205 wae a =<. 
Filaments multicellular, cylindrical and unbranched 
Litosiphon ...p.57 
Free filaments short, of approximately uniform length, standing 
very close together and arising from a one- ei (or occasion- 
ally two-layered) cellular plate (see note 4) . ae She ae 
Free filaments forming hemispherical or cloner tufts, not 
arising from a one-layered basal plate ... oo = ee ae 
Free filaments arising from horizontally creeping threads so a 
Free filaments arising from a dense core of compressed, almost 
colourless, pseudo-parenchymatous tissue tee ite =e, ae 
Free filaments (quarter to half inch long) arising in tufts ; 
plurilocular sporangia formed by transformation and lateral 
extension of intercalary cells of the filaments; unilocular 
sporangia very large arising as lateral branches from the base 
of the filaments ... S05 3: skis Leptonema . ...p. 66 
Free filaments of unequal eae arising irregularly from 
creeping filaments, bearing sporangia as lateral branches 
or terminally, some upright branches may be sterile and 
others transformed into colourless hairs. 
Minute parasitic or epiphytic species of Ectocarpus 
(See note 4asp oso) mie. eg bag shes ae «2p. 68 
Core of closely woven pseudo-parenchymatous tissue covered 
by free assimilatory filaments of approximately equal length, 
bearing sporangia as lateral branches from their bases 
Myriactis ...p.65 
Core of colourless pseudo-parenchyma covered by radiating 
filaments of two kinds :— 
(a) Short club-shaped assimilators, with unilocular and (in 
some species) plurilocular sporangia as lateral branches 
from the base and 
(b) longer branches of much larger cells ... Elachista ...p.65 
Basal plate one cell thick throughout, covered by short, 
unbranched, upright assimilatory filaments; unilocular and 
plurilocular sporangia direct from the basal plate ; plurilocular 
sporangia with one or more rows of loculi Myrionema ...p.68 
Basal plate one cell thick throughout, with or without upright 
assimilatory filaments, but giving rise to sporangia, hairs 
and ascocysts (see note 10); plurilocular sporangia with 
one row of loculi aoe oe ee ... Ascocyclus ...p.69 
