THE ALGM 



101 



b. No vegetative cell-division. 



1. Unicellular forms. Family: Protococcaceae. 



2. Multicellular colonies of definite form. Family : Hydrodic- 



tyaceae. 



Order III. Confervoideae 



The Confervoideae, in their fully developed form, are always truly 

 multicellular, although they not infrequently may vegetate for a long 

 time in a unicellular condition (Palmella stage), which is hardly 

 distinguishable 

 from certain Proto- 

 coccoideae, and this 

 has given rise to a 

 good deal of confu- 

 sion in their classi- 

 fication. While 

 they are mostly 



/ 



FIG. 70. Cells from the 

 thallus of Ulva latis- 

 simu (x500). 



fresh-water plants, 

 some of them, like 

 the Sea-lettuce 

 (Ulva), and species 

 of Cladophora and 

 Chaetophora, are 

 characteristically 

 marine. Others 

 grow in moist air FlG< 71 '~" A > Stigeoclonium tenue (x 100). B, a single 

 cell (X GOO), showing the single chromatophore ; n, nu- 



attached to trees 



^1 



cleus. C, Microspora sp. (X 500). D, Draparnaldia sp. 

 ( X 100) . E, zoospore of Cladophora Jracta ; e, eye-spot ; 

 n, nucleus. F, conjugating gametes of Ulothrix zonata. 

 (F, after DODEL.) 



and other plants. 

 Such, for instance, 

 are the genera Tren- 

 tepohlia, Mycoidea, and others. Still more remarkable is the curious 

 genus Trichophilus, which grows among the hairs of the Sloth (Brady- 

 pus). Mycoidea is a true parasite upon the leaves of various plants. 



