90 BOTANY 



into one ; i.e. there is a true fertilization. From the cell thus formed a new Dia- 

 tom is either formed at once or after a preliminary division of the protoplast. 



Affinities of Diatomaceae 



The Diatoms are not, apparently, closely related to any other group 

 of plants. In their cell-structure they approach the Desmids, one of 

 the lower orders of Green Algse, and in the structure of their shell, 

 and their color, they may show some relation to the Peridinese. With 

 the true Brown Algse they have little in common but their color. 



Fossil Diatoms 



The silicious shells of Diatoms are very resistant, and have been 

 preserved, often in enormous quantities, in a fossil condition. It is 

 remarkable, however, that they are quite unknown from the older 

 formations, and it seems probable that the group as it now exists is 

 of comparatively recent origin. 



Classification of Diatomaceae 



The Diatoms have been divided- into seventeen families grouped 



under two orders. (Schutt, 18.) 



Ord. I. Centricce. Valves usually circular or oval in transverse 

 sections. No raphe. 



Ord. II. Pennatce. Valves bilaterally symmetrical, markings usually 

 pinnately arranged. Raphe usually present. Valves 

 boat-shaped or rod-shaped in most of them. 



BIBLIOGRAPHY 



'87. 1. De Bary, A. Fungi, Mycetozoa, and Bacteria. Oxford, 1887. 



'00. 2. Benecke, W. Ueber Farblose Diatomeen der Kieler Fohrde. Prings- 

 heim. Jahrb. fur wissenschaftliche Botanik, xxxv, 1900. 



'97. 3. Davis, B. M. The Vegetation of the Hot Springs of Yellowstone Park. 

 Science, VI, 1897. 



'97. 4. Fischer, A. Vorlesungen iiber Bacterien. Jena, 1897. 



'87. 5. Goebel, K. Outlines of Classification, etc. Oxford, 1887. 



'99. 6. Green, J. R. Fermentation. Cambridge, 1899. 



'96-1900. 7. Karsten, G. Papers on the Reproduction of Diatoms. Flora, '96, 

 '97, 1900. Biologisches Centralblatt, 1900. 



'98. 8. Kirchner, 0. Schizophycese in Engler and Prantl, Die natiirlichen 

 Pflanzenfamilien. Leipzig, 1898. 



'94. 9. Lister, A. A Monograph of the Mycetozoa. London, 1894. 



'00. 10. Macbride, T. H. The Myxomycetes of North America. London and 

 New York, 1900. 



'96. 11. Migula, W. Schizomycet.es. Engler and Prantl, Nat. Pflanzenfa- 

 milien. Leipzig, 1896. 



