238 
PLANT STUDIES 
is the low type called isogamy, the pairing gametes being 
alike. 
Ulothrix is taken as a representative of the Conferva 
forms, the most characteristic group of Chlorophyceae. All 
4\ *" 
FIG. 205. Ulothrix, a Conferva form. A, base of filament, showing lowest holdfast 
cell and five vegetative cells, each with its single conspicuous cylindrical chloro- 
plast (seen in section) inclosing a nucleus ; B, four cells containing numerous 
small zoospores, the others emptied; C, fragment of a filament showing one cell 
(a) containing four zoospores, another zoospore (b) displaying four cilia at its 
pointed end and just having escaped from its cell, another cell (c) from which 
most of the small biciliate gametes have escaped, gametes pairing (d), and the 
resulting zygotes (e) ; D, beginning of new filament from zoospore ; E, feeble 
filaments formed by the small zoospores : F, zygote growing after rest ; G, 
zoospores produced by zygote. CALDWELL, except F and G, which are after 
DODEL-PORT. 
the Conferva forms, however, are not isogamous, as will be 
illustrated by the next example. 
165. Edogonium. This is a very common green alga, 
found in fresh waters (Fig. 206). The filaments are long and 
simple, the lowest cell acting as a holdfast, as in Ulothrix 
