CONFERVAS 



173 



snow plant" of high mountains and polar regions, a 

 unicellular ciliated organism (Chlamydomonas) which is 

 usually of a red color, and some more common but similar, 

 often red, organisms (Haematococcus) found in pools and 

 on wet earth. They are all more like animals than 

 plants. 



Class 4. CONFERVOIDEAE. Confervas 



241. The Confervas are simple or branched filaments of 

 cells, or a sheet (plate) of cells, and number about 640 

 species. They propagate by (1) the fracture of the 

 filaments (into hormogones), (2) ciliated zoospores, (3) 

 thick- walled spores (chlamydospores), and generate by 

 the union of isogametes or heterogametes, to form a 

 zygote which often becomes a thick-walled spore. They 

 are mostly fresh-water plants, in 

 ponds and in running waters. 



242. The simplest of the Confervas 

 are small unbranched filaments (spe- 

 cies of Ulothrix) which are usually 

 attached by a basal cell ("root"). 

 They propagate by 2- or 4-ciliated 

 zoospores, and generate by the union 

 of 2-ciliate gametes. 



243. The very similar, much-branched and rooted 

 Draparnaldia and Chaetophora present a slightly higher 

 development of the same type. They are common in 

 running fresh water. 



244. Related to these are the Sea-Lettuces common on 

 stones, wharf-timbers, etc., along the coast and in brack- 

 ish waters, and resembling small lettuce leaves. Each 

 plant consists of a single layer of cells (Monostroma) or 

 two layers (Ulva), and nearly every cell is capable of 



Fig. 67. — Ulothrix and 

 Monostroma. 



