22 
IOWA ACADEMY OF SCIENCES. 
and ox-bows. Besides these there are a considerable number 
of ponds. The forms from Fayette, not yet fully studied, are 
preserved in formalin and await further investigation. 
Grinnell lies in a region covered by the very old Kansan 
drift and on 'a divide between the Mississippi and Missouri 
rivers. High elevation and long time have combined to 
give a drainage system so perfect that ponds, other than 
artificial, are scarcely known in the region thus far studied, 
lying near the city. However, five artificial bodies of 
water lie within a mile of the place. A beginning of in- 
vestigation of these has been made, and the present inten- 
tion is to continue the study of the plant plankton, 
carefully noting the increase in number of species of algae 
in these new artificial bodies of water from year to year. 
The streams near the city are all small creeks, but the work 
could in time easily be extended to the Skunk river region, 
ten miles away. 
No special attempt has been made to determine the 
diatoms and desmids, but besides the usual simple forms, 
a number of species consisting of stalked or filamentous 
colonies have been observed. Cosmarium leve Rabh. was a 
common form at Fayette, and other species of this genus 
and several forms of Closterium were frequently seen in 
both localities. 
Two species of Coleochaete, one thalloid and the other 
filamentous, were collected at Fayette. The thalloid 
species we have provisionally called Coleochaete scutata 
Breb., while the filamentous form seemed to be Coleochaete 
soluta Pringsh. The species of this genus are of special 
interest on account of their relationships with higher land 
plants as shown in the segmentation within the ovary 
previous to the formation of the zoospores and in the 
passage from filamentous to thalloid forms. Therefore, 
these plants are of special interest for class work, but it 
may well be doubted whether anyone has ever found any 
species in sufficient quantity for that purpose in the state. 
No previous report of Coleochaetes in Iowa has been made. 
