i68 



FORMS OF DIATOMS 



sluggish streams and often render sticks and stones in the water 

 slippery with slimy deposits. They are widely distributed on 

 damp soil and in fresh and salt waters. Note should also be 



FiG. 94; Common forms of diatoms: A, fan-shaped colonies of diatoms, 

 Licmophora, attached by gelatinous stalks to seaweed. The repeated divi- 

 sion of a solitary diatom gradually builds up the fan-like colonies. B, Tahel- 

 laria, forming colonies grouped in zig-zag blocks. C, Melosira, cylindrical 

 pill-box-like diatoms, arranged in chains. Below end view of the diatom. 

 D, a species of Navicula arranged in gelatinous branches. At right enlarged 

 view of a branch in which the diatoms glide back and forth. — After Wm. 

 Smith. 



made of the peculiar species that float upon the surface of the 

 ocean and form the larger part of that organic life known as 



