THE FUNGI 253 



inward. This constriction may take place in any axis in the 

 spherical bacteria, but in the rod forms it always occurs across 

 the long axis of the cell. The divided protoplast then secretes 

 a cell wall between its two halves, the new wall splits, and the 

 two cells thus formed separate to form two new plants. In a short 

 time the two daughter plants thus formed will reach maturity 

 and divide again. Unless this division process is stopped by lack 

 of food or by other unfavorable conditions, the rapid multiplication 

 mentioned above will result in thousands of new plants in a few 

 hours. It has been estimated 

 that under the most favorable 

 conditions for growth and divi- 

 sion seventeen million bacteria 

 might be produced in twenty- 

 four hours from one bacterial 



cell. This maximum rate of 



TIG. 136. Spore formation in bacteria 



division under such circum- 



a, two bacterial cells ; 6, granules collect- 

 StanceS IS Said to be at the i, lg to form spores; c, black spores in 



rate of One division every two ce " s - After Fisher Redrawn from 



J Marshall's " Microbiology " 



twenty or thirty minutes ; but 



such a maximum, it is safe to say, is never realized in nature 

 for any considerable length of time, or the world would be. over- 

 run with bacteria. 



Spore formation in bacteria (Fig. 136) takes place within a 

 bacterial cell which acts as a spore mother cell. One spore 

 only is formed in each cell, and the process begins by the 

 collection and rounding up of the protoplast in the middle, or 

 at the end, of the mother cell, which often bulges at this point 

 with the accumulation of the protoplast. A new cell wall is then 

 formed around the protoplast within the old mother-cell wall, 

 and the spore is complete, although still within the cavity of 

 the mother cell. These spores remain in a resting condition 

 until favorable conditions for growth arise, when they germinate 

 to form a new plant. In this process the wall of the mother cell 

 is split and the spore wall and protoplast protrude and expand 

 into the form of the bacterium from which the spore sprang 

 (Fig. 137). In the case of the rod bacteria the splitting of the 



