THE FRESH-WATER ALGAE 



171 



245 (243, 244) Structure as in Trentepohlia but many of the cells having 



setae Nylandera Hariot. 



There is but one species of this genus described, and the only 

 point of distinction between this and Trentepohlia is the rather 

 coarse and unsegmented setae. 



FIG. 239. Nylandera tentaculata Hariot. X 140. (After Hariot.) 



246 (191, 196) Plant an attached disc 247 



247 (248) Plant a small, attached disc or cushion of cells, made up of radiating 



rows of cells either separate or grown together, bearing on 

 the surface long sheathed hairs. Reproduction by means 

 of zoospores and by heterogametes. 



Family COLEOCHAETACEAE. 



Only one genus Coleochaete Brebisson. 



Cells with a single, large, parietal chromatpphore and a pyrenoid. Any vegetative cell may 

 give rise to an egg-shaped zoospore. Plants either monoecious or dioecious; opgonia flask-shaped, 

 at the end of a branch or row of cells; antheridia near the oogonia, each bearing a single anthero- 

 zoid ; a layer of cells develop about the oospore. On germination the oospore divides, producing a 

 number of cells, in each one of which a zoospore is formed; these reproduce the parent plant. 



FIG. 240. Coleochaete scutta Br6bisson. Portion of a disc. X about 215. 



248 (247) Plant a disc, of one or more layers in thickness, adhering through- 

 out to a substratum, often bearing gelatinous hairs. Repro- 

 duction by means of zoospores, and in some instances by 



isogametes Family MYCOIDEACEAE. 



Only one genus recorded here Ulvella Crouan. 



Plant a disc of radiating rows of cells, a single 

 layer in thickness on the margin and several in the 

 middle; chroma tophore single, but thickened so as 

 to give the appearance of many; pyrenoid single. 



Appearance much as in Coleochaete except that mem- 

 brane and hairs are more gelatinous and the hairs 

 have no sheaths. Reproduction by zoospores only. 

 These have cilia, and arise first at the center of the 

 disc and later toward the margin. On the surface of 

 water plants. Mr. F. S. Collins believes this to be 

 Chaetopeltis but sexual reproduction characteristic for 

 Chaetopeltis has not been observed in this form. 



FIG. 241. Ulvella americana Snow ( = 

 Pseudulvclla americana Willc). X 150. 

 (Original.) 



