310 THALLOPHYTES 
cell, they so arrange themselves and grow together at points of 
contact as to form a miniature net. Through the softening and 
decay of the wall of the mother cell, the small net is set free 
and by the mere enlargement of its cells becomes a colony of 
adult size. The gametes are isogamous and are formed in great 
numbers by certain cells. As many as 100,000 of them may be 
produced within a cell. Almost as soon as formed they escape 
from the mother cell and begin to pair 
and fuse. The zygospore produces 
zoospores which at first pass into a rest- 
ing stage and later from new nets. 
Thus in the Protococcales the individ- 
uals may remain separate or form colo- 
nies which are exceedingly complex in 
the higher forms. In the simplest forms, 
as Pleurococcus illustrates, reproduction 
is by cell division in which the parent 
divides to form two new plants, but in 
the higher forms there is reproduction 
Fig. 266. — Sea Lettuce = 7 i 
(Ula), a Confervoid Alga by zodspores and isogametes. Since 
having a plate-like plant their sexuality does not reach the heter- 
body. This plate-like plant ogamous condition, they are not so ad- 
body is two layers of cells vanced in this respect as the Volvocales 
int, Yolichmesss. Mei Green, are, but they lack motility and this 
and resembles a leaf in 
form. Natural size. Re. feature is characteristic of the higher 
drawn from Bessey. plants, which are adapted to live on land 
rather than in the water. 
Confervoid Algae (Confervales).— The Confervales or Con- 
fervoid Algae are among the most familiar of the Green Algae. 
Their plant bodies are usually filaments, commonly consisting 
of much elongated cylindrical cells closely joined end to end in 
a single row. The filaments may be several inches in length 
and in some forms much branched. In a few forms the plant 
body is plate-like instead of filamentous, as the Sea Lettuce illus- 
trates (Fig. 266). The Confervales are common in lakes, ponds, 
streams, and water troughs, where many of them grow attached 
and form green hair-like fringes about rocks and other ob- 
jects. More than 700 species of them are known, and there 
is considerable variation in plant body and methods of repro- 
duction. 
