PROPAGATION BY SPORES. 163 



The spores can germinate and form bacilli in suitable Germination 

 nutrient solutions and at a proper temperature ; but this 

 seldom occurs in the same solution in which the spores 

 were formed, nor till after a considerable period of rest. 

 According to Koch, when the process of germination 

 begins the clear spherical mass in which the spores 

 are embedded becomes egg-shaped, and then elongated, 

 while the spore becomes pale and finally disappears. 

 According to Prazmowski and Brefeld the spores swell 

 in the first place, become pale and lose their dark 

 contour and the clear area around; then half-moon 

 shaped dark shadows either appear at each end, and the 

 spore, which is in a state of trembling, dancing move- 

 ment, sends out a projection on one side like a papilla 

 which subsequently grows out to form a rod ; or in other 

 cases the germinating tube .so\ ^ 



passes out in the direction of ~ c c? &$ 



the long axis of the Spore, Fig 37.- Germination of spores 



the spore membrane having x 80 - 



become uniformly thickened in its whole circumference. 



The endosporium then becomes the cell wall of the 



young shoot, while the discarded exosporium usually 



remains for a considerable time near the newly formed' 



rod. 



In the case of the bacteria which form arthrospores so-called 

 the fructification simply occurs by individual members arthrospores. 

 of a chain or of a mass of bacteric cells showing greater 

 vitality than the rest ; there is often no morphological 

 difference to be noted between them and the other 

 -bacteria in the same chain, while at other times the .cells 

 destined for the maintenance of the species appear to* 

 become somewhat larger, thicker walled, and filled with 

 denser and more highly refracting protoplasm. While 

 the remaining cells of the group die, these segments 

 form the commencement of new groups (de Bary). 



Most spores, especially those formed endogenously, Besisting- 

 have the character of resting cells, which are more re- p ower of tllc ' 



true spore. 



sistant than the vegetative cells of the same species. 

 Some are extraordinarily resistant, can even withstand 

 boiling in fluids for several minutes, and are only slowly 



