Diatoms 



115 



Campylodiscus {0 and p) is a saddle-shaped diatom of 

 rather local distribution. It is found abundantly in the 

 ooze overspreading the black muck bottom of shallow 

 streams at the outlet of bogs. In such places in the 

 upper reaches of the tributaries of Fall Creek near 

 Ithaca it is so abundant as to constitute a large part of 

 the food of a number of denizens of the bottom mud — 

 notably of midge larvae, and of nymphs of the big 

 Mayfly, Hexagenia. 



These are a few — a very few — of the more important 

 or more easily recognized diatoms. Many others will 

 be encountered anywhere, the littoral forms especially 

 being legion. Stalked forms like Cocconema (fig. 353 and 

 fig- 37) will be found attached to every solid support. 

 And minute close-clinging epiphytic diatoms, like 

 Cocconeis and Epithemia will be 

 found thickly besprinkling the 

 green branches of many sub- 

 merged aquatics. These adhere 

 closely by the flat surface of one 

 valve to the epidermis of aquatic 

 mosses. 



In open lakes, also, there are 

 other forms of great importance, 

 such as Diatoma, Fragillaria, etc., 

 growing in flat ribbons, as does 

 Tabellaria. It is much to be 

 regretted that there are, as yet, 

 no readily available popular 

 guides to the study of a group, 

 so important and so interesting. 

 Equipped with a plancton net and a good microscope, 

 the student would never lack for material or for prob- 

 lems of fascinating interest. 



Fig. 37. A stalked colony 

 Cocconema. 



