RHODOPHYCE.E, OR FLORIDE.E 213 



occurrence among Algae. 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. 

 Polysiphonice, 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, arid on this outside 

 cushion the tetraspores and cystocarps are borne. 

 From his discovery and minute study of the latter 

 in Ch. Polysiphonice, Richards has determined the 

 position of this genus to be within Chcetangiece 

 rather than Gelidiece, as placed by Schmitz in his 

 system. Ch. Polysiphonice grows in the axils of the 

 branches of Polysiphoyiia 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, b 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. Chcetangium 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. 



