SIGNIFICANCE OF SHELL STRUCTUKE IN DIATOMS 



By Paul S. Ck)NGER 



Research Associate, Carnerjie Institution of Washington 



Custodian of Diatoms, United States National Museum 



[With 19 plates] 

 "maximis in minimis" 



In this day of rapid industrial change and advancement, of new 

 and novel ideas, and of strange and futuristic tendencies in design, 

 when it is a question how quickly the next idea will become obsolete, 

 and when there is much discussion as to whether in a few years we 

 shall be living in houses of steel, paper, or glass, it is interesting to 

 take note of a large group of small plants that have been living for 

 30,000,000 years or more in glass houses and still find this a very 

 successful type of abode, literally building about themselves walls of 

 glass and frequently elaborating these walls in beautifully sculptured 

 and highly ornamental architectural designs. These are the diatoms, 

 of which there are more than 10,000 different kinds. They are all 

 single-celled or colonial plants. 



If we were to adopt this kind of structural material, everyone's 

 affairs would be even more subject to discussion than they are at 

 present; curtain and venetian-blind manufacture would constitute 

 one of our major industries. But for the diatom, as for all other 

 plants, exposure to the light is a necessity. They have the advantage 

 of being so small that, with few exceptions, they cannot be seen with 

 the unaided eye; hence, though they have lived and continue to live 

 this transparent existence all about us, in every damp spot, every 

 roadside pool, river, lake, and ocean — resting or crawling on the bot- 

 tom, attached to submerged objects, and floating suspended in the 

 water — in unbelievable numbers, it is practically only within the 

 last 100 years that we have become acquainted with them at all. Few 

 diatoms are larger than 1 millimeter, that is, one twenty-fifth of an 

 inch in diameter, and most frequently they are less than one-tenth 

 that size, or one two-hundred-and-fiftieth of an inch. The details of 

 their structure are often exceedingly minute, comprising the most 

 delicate and perfect sculpturing in glass, or, to be exact, in silica. 



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