THE ECONOMIC IMPOETANCE OF THE DIATOMS. 



By Albert Mann. 



[With 6 plates.] 



Scientific study is constantly giving emphasis to the fact that in 

 nature there is little, if any, relationship between size and impor- 

 tance. Charles Darwin long ago made it plain that among the myriad 

 of living creatures the earthworm plaj^s a very important role in the 

 economy of nature, especially as applied to mankind, and is in fact 

 a greater animal than the elephant. The lowly grass outweighs in 

 importance the loftiest tree of the forest. A brilliant series of dis- 

 coveries led by Pasteur has revealed to us that the most gigantic 

 ])ower, in some cases beneficent, in others baleful, is exercised by 

 the minutest of all living things, the bacteria. It is, therefore, not 

 to be wondered at that the plants here under consideration, although 

 as a class quite invisible to the naked eye, and many of them so 

 minute that a hundred can be laid upon the head of a common pin, 

 are at the same time of great economic importance. 



But for a long time the attention of mankind was diverted from 

 the more practical values that we are here to consider by that most 

 striking characteristic of these plants, their surprising beauty and 

 the unequaled complexity of their ornamentation. Coupled with 

 their minuteness there is a daintiness of structure and an artistic 

 diversity of design among the six thousand and odd species which 

 has doubtless been the cause why until recent times they have been 

 objects of merely esthetic interest. They have never been neglected, 

 for from the time of the invention of the microscope they have been 

 the darlings of the microscopists ; but only to-day are they begin- 

 ning to be recognized as an important factor in the welfare of the 

 human race. 



Each diatom plant secretes for itself an incasing box or invest- 

 ment of pure silica, somewhat as a clam or oyster secretes its shell; 

 and these crystalline walls, within which the tiny living plant is 

 housed, are sculptured and carved with such bewildering complexity 

 of design and yet with such perfection of finish that their attrac- 

 tiveness has absorbed the attention of students to the detriment of 

 their many less spectacular qualities. 



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