RHODOPHYCEA, OR FLORIDEA 213 
occurrence among Alge. Instead of killing the 
cells of the host affected, its parasitism appears to 
stimulate them to greater activity, as in the cases 
of hypertrophy caused by fungal parasites. Ch. 
Polysiphonie, if not a complete parasite is at least 
a partial one, and injuriously affects its host. These 
parasitic plants form exceedingly minute cushions 
of tissue externally while sending rhizoid filaments 
into the interior of the host, and on this outside 
cushion the tetraspores and cystocarps are borne. 
From his discovery and minute study of the latter 
in Ch. Polysiphonie, Richards has determined the 
position of this genus td be within Chetangiee 
rather than Gelidiew, as placed by Schmitz in his 
system. Ch. Polysiphonie grows in the axils of the 
branches of Polysiphonia fastigiata, and its rhizoid 
filaments penetrate and establish intimate connec- 
tion, especially with the axial row of cells. The 
tetraspore-bearing plants exhibit certain differences 
in the peripheral thallus-cells from those of the 
cystocarpic plants (see Fig. 64, 6 and c). 
The Geographical Distribution is confined to the 
temperate and tropical seas. Scinaia and Choreocolax 
are the only British genera, though they have other- 
wise a wide range. Chetangiwm occurs at the Cape 
of Good Hope, and Galaxaura and Actinotrichia are 
tropical and subtropical, the former being repre- 
sented by one species in the Mediterranean. 
