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. 
Crass 4. CONFERVOIDEAE. CoNnFrervas 
241. The Confervas aresimple 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 ; 
° Fic. 67.—Ulothrix and 
zoospores, and generate by the union Monostroma. 
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 
