312 



BOTANY 



Among the parasitic Bacteria there are numerous forms which may be described 

 as harmless, as for example Sarcina ventriculi (Fig. 232, A), which forms cubical 

 masses of cocci in the stomach and intestines of man ; also the various Bacteria, 

 Micrococcus, Spirillum dentium, Leptothrix huccalis, etc. (Fig. 4, p. 11), which 

 occur in the cavity of the mouth. Of dangerous or pathogenic Bacteria which 

 have been demonstrated to be the cause of infectious diseases, mention may here be 

 made of the following : Bacillus Tuberculosis, the cause of tuberculosis (Fig. 232, G) ; 





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Fig. 231. — Leuconostoc mcsenterioidcs. A, Iso- 

 lated spores ; B, C, formation of chain of 

 cells with gelatinous sheath ; D, portion of 

 mature zooglcea ; E, formation of spores in 

 the filaments of the zoogloea. (After Van 



TlEGHEM, X 520.) 



Fio. 232. — A, Sarciiw. ventriculi (X700); B, 

 Spirochaete Obermeieri (x950); C, Bacillus 

 Tuberculosis, plasmolysis of contents occa- 

 sioned by mode of treatment ( X 1500) ; D, 

 Vibrio cholcrae ( x 950) ; E, Streptococcus 

 pyogenes ( x 050). (After Baumgarten.) 



Vibrio cholerae asiaticae, the comma bacillus of Asiatic cholera (Fig. 232, D) ; 

 Spirochaete Obermeicri (Fig. 232, B), found in the blood of patients suffering from 

 intermittent fever ; Bacillus Typhi, the bacillus of typhoid fever ; the pyogenic 

 Bacteria, Streptococcus pyogenes (Fig. 232, E) and Staphylococcus aureus ; Strepto- 

 coccus Erysipelatis, occurring in the lymphatic glands of persons affected with 

 erysipelas ; Bacillus Anthracis, the anthrax bacillus, with a mode of spore- formation 

 similar to that of the Hay bacillus. 



Rhizobium Leguminosarum- (Bacillus radicicola) lives in symbiosis with the 

 Leguminosae, and causes the formation of their root-tubercles. After multiply- 

 ing enormously in the cells of the root-tubercles, the Bacteria eventually undergo 

 transformation into bacterioids (see p. 211). 



Class III 



Diatomeae (Diatoms) 



The Diatomeae constitute a large class of unicellular Algae, 

 including about 1500 species. They usually occur associated together 

 in large numbers, in both fresh and salt water, and also on damp 

 soil. 



The individual cells or FRUSTULES are either solitary and free- 

 swimming, or they are attached by means of gelatinous stalks, excreted 



