CHAPTER IX 



SCHIZOMYCETES. BACTERIA 



Chester, F. D. A Manual of Determinative Bacteriology. 401 pp. 190 figs. 

 Migula, W. System der Bakterien 1: 368 pp. 6 pis. 1897; 2: 1069 pp. 



18 pis. 1900. 

 Smith, Erw. F. Bacteria in Relation to Plant Diseases. Carnegie Inst, of 



Washington, Publication 27 (Vol. I): 285 pp. 31 pis. 145 figs. 1905. 

 Van Hall, J. J. Bijdragen tot de kennis der Bakterieele Plantenziekten. 



197 pp. 1902. Amsterdam. 



The Schizomycetes, or fission fungi, better known as the 

 bacteria, embrace numberless species of microorganisms which 

 are, perhaps, morphologically the simplest of the fungi. These 

 organisms consist of minute single cells, and while the cells 

 may often be arranged in chains or filaments, loosely associated 

 in colonies, or temporarily bound together in sheaths, there is 

 no case in which an individual may be looked upon as more 

 than a single cell. The cell forms of these organisms may be 

 constantly assigned to one of only three general types, namely, 

 spherical (Coccus type), rod-like (Bacillus type, varying from 

 spheroidal to long rod-shape), and spiral (Spirillum type or screw 

 form). The diameter of the cells of the coccus forms may vary 

 from .3 to 3 fi (micromillimeters), and of other forms from 

 .3-4 X 1-20 n, the maximum being attained by the screw form. 

 These organisms play an exceedingly important role in the econ- 

 omy of nature. The great majority are saprophytic, yet many 

 species induce diseases of animals. A relatively small number 

 of species included in a single family (so far as present knowl- 

 edge goes) produce diseases in plants. These diseases, however, 

 rank among the most important both on account of the destruc- 

 tive action of these organisms and the great difficulty experienced 

 in attempting to develop effective means of control. The number 

 of phytopathological forms is annually augmented, and it is proba- 

 ble that they will be reckoned as relatively more important as 

 further investigations are made. 



103 



