IOWA ACADEMY OP SCIENCES. 
51 
East Okoboji Lake is composed of three small lakes in a 
chain, the water varying from three feet in the upper one to 
eighteen or twenty feet in the lower one. The deposit varies 
also from eight feet in the upper to a much greater depth in 
the lower. Here there is a much greater percentage of sand 
than in Clear Lake, due to more extended surface drainage 
and steeper hills. 
The channel, however, which connects East Okiboji and 
West Okiboji Lakes, is the most remarkable place of all. 
Remarkable, not only for the number of diatoms, but for a 
host of other aquatic forms growing in the most lavish pro- 
fusion. The conditions here are certainly very favorable for 
plant growth. High hills, covered with trees, protect the 
channel from the winds, an*d its form precludes the possibility 
of large waves. Then, too, a gentle current sets from one 
lake to the other, keeping the water in fine condition. In the 
fall, after the larger plants have passed their perfection and 
have begun to die, the diatoms overrun them all and, indeed, 
every other thing below the surface of the water. The com- 
mon bladderwort becomes the home of vast colonies of the 
stalked forms, as cocconema, gonphonema, bands of fragil- 
laria, with long, acicular synedra intermingled. Acres are 
thus covered, where there are no large waves and the water is 
not too deep. In those parts of the lake where rushes grow, 
each one is covered below the water line with a layer a half an 
inch or more in thickness. 
Across this channel a railroad was built, and in so doing a 
diatomaceous deposit was found fifty-two feet deep 
In West Okiboji Lake water was found 125 feet deep, the 
deposit being of unknown depth. So soft and yielding is this 
material that a dredge, weighing only two or three pounds, 
when dragged along the bottom sinks into it to a depth of ten 
or twelve feet. 
In comparing the species found here with those found in 
Clear Lake, both lying in the same geological formation and 
no great distance apart, it is seen at a glance that they are 
utterly different. In Clear Lake such genera as suriraya, 
navicula, cymbella, eunotia pleurosigma and cymatopleura 
are found, as compared with cocconema, odontidium, stictodis- 
cus and synedra in Okoboji Lake. 
Silver Lake also adds a small quota, but has not been care- 
fully examined. 
