THE AMERICAN 



MONTHLY 



MICROSCOPICAL JOURNAL. 



YoL. XII. 



MAY, 1891. 



Ko. 5. 



All communications for this Journal, whether relating to business or to editorial 

 matters, and all books, pamphlets, exchanges, etc., shojtld be addressed to Ameri- 

 caii Monthly Microscopical Journal, Washington, D. C. 



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 by International Postal Order Jor $i.i^ per anttum, or they may be sent to Messrs. 

 Triibner &^ Co., j/ Ludgate Hill, London, or to Mr. W. P. Collins, /j/ Great 

 Portland street, London, accompanied by the yearly price o J five shillitigs. 



Diatoms : Their Life History and their Classification. 



By Rev. FRED'K B. CARTER, 



MONTCLAIK, N. J- 



[With Frontispiece.] 

 ( Continued from page. iSj. ) 



We come now to the last point, hoxv to tell to xvJiat geinis a given 

 diatom beloitgs., and my answer is, by not attempting too much at 

 once, but attacking the classification in sections. Diatoms, like des- 

 mids, are unicellular algte. But unlike the desmids, they are salt-water 

 as well as fresh-water plants. No desmids are found in salt water. 

 Nearly as many genera of diatoms are found in salt water as in fresh. 

 Others are both fresh-water and marine, and still others are only found 

 fossil. Let us suppose, therefore, that a person wishes to know the 

 forms he meets with in his gatherings from the ponds and ditches. In 

 that case the fossil and the exclusively marine forms may be disregarded 

 by him. Now, this simplifies the matter very much. For example, in 

 the micrographic (which, for the same reason as was given in regard to 

 the Rhizopods, we follow in preference to any later system of classifi- 

 cation) there are over loo genera of diatoms enumerated, or about five 



List of Figures in the Frontispiece. 



Fig 



1. Tetracyclus lacustris. 



2. 'I'abellaria flocculosa. 



3. Terpsinoe inusica. 



4. Pleurosigma angulatum. 



5. Stauroneis phcenecenteron. 



6. Acnanthes subsessilis. 



7. Navicula (Pinnularia) nobilis. 



8. Amphora robusta. 



9. Gomphonema acuminatum, var. laticeps. 



10. Cocconeis scutellum. 



11. Cymbella gastroids. 



12. Navicula cuspidata. 



13. Meridion circulare. 



14. Epithemia turgida. 



15. Eunotia robusta, var. diadema. 



Fig. 16. Eunotia (Himantidium) pecturalis, var. 

 elongata. 

 17. Diatoma vulgare. 

 i8. Asterionella formosa, var. gracillima. 



19. Uenticula lauta. 



20. Odontidium hyemale. 



21. Fragilaria capucina. 



22. Melosira nummuloides. 



23. Cyclotella operculata. 



24. Stephanodiscus Niagara. 



25. Campylodiscus costatus. 



26. Cymatopleura solea. 



27. Surirella splendida. 



28. Nilzschia lanceolata. 



29. Amphipleura pellucida. 



Copyright, 1891, by C. W. Smiley. 



