MAJOR VEGETATION OF LAKE OKOBOJI 
97 
Ceratophyllum seems also to enjoy relative immunity to annoy- 
ing algae. The gelatinous species of Rivularia do not adhere to 
it in great numbers as compared with Myriophyllum and others 
that are fairly swamped by these epiphytes. Similarly, since 
Ceratophyllum typically remains submerged it does not offer an- 
chorage to .the free floating filamentous forms which make so 
much trouble for plants that bring their flower stalks to the 
surface. 
Algae regularly enter all these assemblages of seed plants and 
play an important part, usually to the detriment of the larger 
plants. Cyanophyceae, especially Rivularia, attach to all their 
submersed parts, except that Ceratophyllum has partial immunity. 
These epiphytes must seriously interfere with their functions as 
frequently a large part of the leaves and stems is gummed over 
by them. As noted above the filamentous algae form extensive 
masses over shallow waters where the flower stalks and other 
parts of submersed plants project above the surface. In quiet 
water Rhisoclonium forms heavy ‘‘blankets” that bring disaster 
to all entangled forms. 
The Chara beds are very extensive, covering hundreds of acres 
of the bottom of Lake Okoboji. Their biological significance is 
rather obscure. Animals seem not to eat them freely and these 
formations constitute what might be called the desert areas of the 
lake. Studies of the Chara beds are being taken up to determine 
their extent, the component species, depth relations, etc., and to 
outline their relations to other plants and to animals. They con- 
stitute one of the unknown factors in the life of Lake Okoboji. 
These “water weeds” sustain a very close relation to the whole 
question of fish in these lakes. The results of this survey are 
merely preliminary to the more intensive and detailed study of the 
various parts of Lake Okoboji and the other lakes of the group. 
It is of some significance at least that during the entire month 
given to this survey, and during which time hundreds of people 
were observed fishing in various parts of Lake Okoboji, no fish 
were being caught except in or along the edge of these masses of 
major vegetation. 
Department oe Botany 
State University oe Iowa. 
