86 MORPHOLOGY AND CULTURE OF MICROORGANISMS 



When these spores are brought under favorable conditions of 

 moisture, temperature, and food supply, they germinate. There are 

 several types of germination (Fig. 65). In some cases the spore wall 

 ruptures at the pole and the young cell emerges so that its long axis is 

 in the same direction as the long axis of the spore. In another type 

 the spore ruptures equatorially and the young cell emerges with its 

 long axis at right angles to the long axis of the spore. In still another 

 type the spore swells and the young cell absorbs the wall of the spore. 



In the lower bacteria only a single spore is formed in a cell. 

 In the case of the higher bacteria, however, a number of spores may be 

 formed at the distal end of the filament. These are spoken of as 

 conidia, and possess properties similar to those of the endospores. 



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FIG. 65. Spore germination, a, Direct conversion of a spore into a bacillus 

 without the shedding of a spore- wall (B. leptosporus) ; b, polar germination of Bact. 

 anthracis; c, equatorial germination of B. suUttis; d, same of B. megatherium; e, same 

 with "horse-shoe" presentation. (After Novy.) 



In some cultures of bacteria, as for example in the micrococci, 

 certain cells seem to be larger and different from the other cells. In a 

 streptococcus filament, certain cells suggest to the observer the joint 

 spores of the algae and have therefore been spoken of as arthrospores or 

 joint .spores. There is, however, no evidence of an experimental 

 nature, which warrants the belief that these cells are in reality spores, 

 and it must be said that at the present time the presence of arthro- 

 spores among the bacteria is purely hypothetical. 



CELL GROUPING* 



Bacteria rarely occur singly but usually in groups. These cell 

 aggregates are frequently very constant and quite characteristic of the 

 organism possessing them. They are of sufficient definiteness and 

 constancy to be used by the systematists in characterizing large groups. 



^Prepared by W. D. Frost, 



