172 PHYLUM II. CHLOROPHYCEAE 
sites (Family Synchytriaceae) in the tissues of other algae, 
or even land plants, and are known as Gall-fungi. 
ORDER COENOBIALES 
238. The cells or coenocytes in these plants are aggre- 
gated into colonies, the most common of which are the 
pretty species of Scenedesmus, in 
which four spindle-shaped cells lie 
side by side. Less common is the 
very regular plate-colony of Pedias- 
trum with usually a dozen or more 
regularly arranged coenocytes. Re- 
pF, 66-—Seenedesmus id mi ee is. a Water Net 
pee ydrodictyon) with its many long 
coenocytes arranged in a_ hollow, 
reticulated colony 20 to 30 centimeters long. Ciliated 
zoospores and isogametes occur in Pediastrum and 
Hydrodictyon. 
239. Here are commonly placed certain doubtful 
organisms, the Volvoces (Volvox, Pandorina, and related 
genera), with the color of plants but the structure of 
animals. Most botanists still claim them on account of 
their color, but many zoologists emphasizing the impor- 
tance of their structure regard them as animals (Flag- 
ellata). The explanation here given is that at about 
this point in the Vegetable Kingdom the animal type be- 
came differentiated from the plant type by an increase 
in the motility of the cells, and in the Volvoces we have 
the organisms on the pathway leading from plants to 
animals. In the opinion of the authors they have already 
passed the frontier of the Plant Kingdom, and entered 
that of Animals, although they have not yet abandoned 
their use of chlorophyll. 
240. On the same ground should be excluded the “‘red 
