i66 



FRESH-WATER BIOLOGY 



224 (227) Branches abundant 225 



225 (226) Plants large, tufted; reproduction by zoospores. CladopkoraKvLtzing. 



Plant frequently very large; diameter of the filaments 

 much greater at the base than at the ends; the length of the 

 cells one to twenty times the diameter; reproduction by 

 zoospores, many being formed from a vegetative cell; these 

 with two or four ciha. 



The number of species of Cladophora is very large, and 

 they are found in fresh, brackish, and salt water, but prob- 

 ably in the greatest abundance along the shores of lakes 

 where they are constantly washed by the waves. Some 

 species are beUeved to be annual and some perennial. 



Fig. 226. Cladophora glomerata KUtzing. X 85. (Original.) 



226 (225) Plant forming pulvinate coatings, cells of two kinds, one Hght and 

 one dark Chlorotyliwm Kiitzing. 



Plant of erect, branching, parallel filaments, forming firm, dense tufts imbedded in a gelatinous 

 mass. In each filament several cells with dense chlorophyll alternate with longer ones contain- 

 ing less chlorophyll, thus giving a concentric arrange- 

 ment of light and dark. 



Chromatophore band-shaped, asexual reproduction by 

 biciliate zoospores which are formed in great numbers 

 in each zoosporagium. Akinetes are also formed. 



Fig. 227. Chlorotylium cataractarum 

 Rabenhorst. X 150. (After Raben- 

 borst.) 



227 (224) Branches not frequent, rarely wanting 228 



228 (229) Branches long, scattered; reproduction by resting spores. 



Pithophora Wittrock. 



Cells long, cylindrical; akinetes formed 

 by the end of a cell being separated by a 

 membrane, the contents becoming much 

 thicker and darker, while the membrane 

 increases in thickness and the whole be- 

 comes swollen in the middle. 



Fig. 228. Pithophora kewerisis Wittrock. a. 

 vegetative filament; b. formation of resting 

 spore. X 140. (After Wittrock.) 



229 (228) Branches short, attenuated, infrequent, sometimes rhizoid-like, 



sometimes lacking altogether. . . Rhizodonium Kiitzing. 



Filaments attached, often curved 

 and matted, usually with short infre- 

 quent branches which consist of one 

 or more cells, sometimes resembling 

 rhizoids. Cell walls lamellose. 



Chromatophore netted, with sev- 

 eral pyrenoids. Nuclei several Re- 

 production by biciliate zoospores 

 „, . , . , . , , . „ . and by akinetes. Sometimes occur- 



RhKcclontumhteroglyphuum KUUing. X 300. ring on damp ground. 

 (Onginal.) 



FlO. 329. 



