CHAPTER VIII 
PHYLUM II. CHLOROPHYCEAE* 
THE SIMPLE ALGAE 
232. The plants of this phylum while still small, and 
mostly microscopic and consisting of single cells, fila- 
ments or rarely plates of cells, show a considerable ad- 
vance over the Slime Algae in having well-defined nuclei, 
definite plastids, a dominant yellow-green color (chlor- 
ophyll and carotin), and in many genera 
sexual reproduction. The cells are much 
better developed, the walls are composed of 
cellulose, and are usually firmer. The nu- 
Fre. 64.—A Clear matter of the cell is collected into a 
coovace © definite nucleus which is surrounded by a 
membrane. A portion of the protoplasm is 
set off as one or more distinct plastids (chloroplasts) 
which are stained green by chlorophyll. 
233. Here the dominant idea is the definite nucleus 
limited by a nuclear membrane. With this are associated 
the definite plastids, true chlorophyll, firm cell wall, 
motile reproductive structures (zoospores and gametes), 
and the still simple plant body. 
234, The Simple Algae, of which there are about 1100 
species, are mainly fresh-water plants, living on wet 
rocks, moist walls or tree-trunks, etc., or floating or 
attached in the deeper waters. A few have become 
degenerated through parasitism. 
* This name is here used in the narrower sense, excluding the 
plants of the phyla ZyaopHycrar and SIPHONOPHYCEAE. 
170 
