THE FRESH-WATER ALGAE 



163 



Plant in early stages like Vlothrix, later forming 

 a slender, solid parenchymatous filament; reproduc- 

 tion by zoospores, one from each cell. 



Quantities of the zoospores are liberated from a 

 filament at a time, the walls becoming partially gelat- 

 inous, but showing a parenchymatous structure after 

 the liberation. 



By some European writers the genus is regarded as 

 the same as Ulolhrix, but forms such as are found in 

 America must establish it as a separate genus. The 

 zoospores have four cilia and a pigment spot, as in 

 Vlothrix; the vegetative cells may change into resting 

 spores. 



Schhomeris has been found growing on river banks 

 and in quiet fresh water. 



Fig. 215. Schizomens leibleinii EUtzing. a. portion of 

 filament. X about 625. b. portion of filament showing 

 division in all directions. X 300. c. zoospores. X 635. 

 (Original.) 



205 (200) Filament with gelatinous envelop 206 



206 (209) Cells not in distinct pairs 207 



207 (208) Cells oval, gelatinous envelop homogenous. 



Hormospora Brebisson. 



This is regarded by many as being but a 

 phase in the development of Vlothrix. but the 

 very gelatinous membrane, the rounded ends 

 of the cells, and the fact that this form is not 

 known to reproduce by zoospores would indi- 

 FiG. 216. Bornwsporamatabths'BTihismn. X about gate that it is an independent genus. 

 600. (Original.) 



208 (207) Cells rounded. Gelatinous sheath showing radial fibrillar struc- 



ture Radiofilum Schmidle. 



Chromatophore single, parietal, with one pyrenoid. 

 Cells spherical, ellipsoidal, or lenticular, in some 

 species united by short necks. Filaments unbranched. 

 Reproduction by simple division. Wille includes 

 Hormospora and Radiofilum with Geminella, a genus 

 not known to occur in America. 



Fig. 217. Radiofilum Jlavescens West. 

 X 300. (After West.) 



209 (206) Cells mostly in pairs. 2ro 



210 (211) Cells rounded, gelatinous substance lamellate, invested by the 



antecedent mother-membrane. . . . Binuclearia Wittrock. 

 Filaments attached when young; each cell pair 

 originates from the contents of a single cell, and is 

 surrounded by a more or less lamellate substance, 

 about which the original membrane is still visible. 

 Chromatophore parietal, reproduction by division 

 and akinetes. 



Fig. 218. Binuclearia tetrana Wittrock. X about 450. 

 (Original.) 



211 (199, 212, 213) Chromatophore axial, with rounded clear spaces at each 



end Planktonema Schmidle. 



Filaments short, free-swimming. Cells cylindrical, rounded at the ends, mostly in pairs, 

 each pair separated from the next by an apparently empty space. Reproduction by division 

 within the membrane after which the parts become separated, probably by a gelatinous sub- 

 stance. 



