48 IOWA ACADEMY OF SCIENCES. 



truth in the remark made by another botanist, with a sniff, 

 that you might as well try to classify wall paper. The diffi- 

 culty, however, is not greater than in other orders of equal size. 



At first it might appear that the state of Iowa, with its 

 monotonous rolling prairies would offer little diversity of 

 aquatic plant life, but this has not proved to be the case. For 

 present purposes the various localities where diatoms are 

 found may be grouped in four divisions. 



First. — Creeks and rivers, with the bogs and old river chan- 

 nels connected with them. 



Second. — Springs, with the bogs and ditches watered by 

 them. 



Third. — The lakes found in that portion of the state covered 

 by the Wisconsin drift. 



Fourth. — Fossil deposits. 



The first localities named, the creeks and rivers, were the 

 first from which material was collected. Here abound the 

 smaller naviculse, synedree, melosirse, and most abundant of 

 them all, the gomphonemsD, which may be seen as long, gela- 

 tinous streamers of a rich brown color, in moving water, or as 

 a covering on the stones in rapids and cataracts. In the 

 brooks and ditches the more fragile forms of nitzschia and 

 synedra are found. Under favorable conditions these little 

 organisms cover the bottom of the brooks and ditches to a 

 depth sufficient to color everything a rich brown. When the 

 sun shines on them the oxygen liberated raises them to the 

 surface of the water and they are carried along until they 

 strike a twig or board or other obstacle, where they may be 

 seen at times an inch in depth and several square feet in 

 extent. 



East of Iowa City, about two and one- half miles, there is a 

 prairie slough, having in it at one point a broad and shallow 

 basin, where the water stands a greater portion of the year. 

 In the month of June this presents to the diatomist at least, a 

 most remarkable appearance. In this basin, covering an 

 extent of about an acre, and to the depth of eight or twelve 

 inches, is a fiocculent seal brown mass of living diatoms. Here 

 Fragillaria virescens stretches its tiny ribbons, and Meridion 

 intermedium spreads its miniature fans in numbers innumerable. 



In the northern portion of the state, where the rivers are 

 but little more than motionless lagoons, the amount of aquatic 

 material is indeed prodigious. In such quantities do algse, 



