86 PLANT LIFE. 



may be corisidered as characteristic of the Protophyta, we 

 nevertheless meet with indications of the multicellular type 

 of structure, and also of the simplest form of sexual 

 reproduction by conjugation. 



Class L— Schizomycetes (^Bacterid). 



The exceedingly minute size of the cells constituting the 

 members of the present group preclude an exact study of 

 their nature. With very rare exceptions chlorophyll is 

 absent ; hence they are either saprophytes or parasites. In 

 one species, Beggiatoa roseo-fersicina, a red colouring matter 

 tinges the protoplasm, and in many other examples, in cer- 

 tain stages of development, bright colours are produced ; but 

 owing to the minute size of the cells, it has not been clearly 

 determined whether the colour occurs in the cell-contents 

 or in the substratum. The individual Bacteria vary in 

 shape from a sphere to an elongated cylindrical rod, the 

 latter being either straight or curved, and some species show 

 a transition from the spherical to the elongated form. Not 

 unfrequently numerous individuals form large gelatinous 

 masses. 



The Bacteria are divided into two groups, based on the 

 mode of reproduction. Endosporous Bacteria reproduce 

 themselves by spores formed within the cells ; Arthrosporcus 

 Bacteria do not form spores, but reproduce themselves by 

 breaking up of the rods into short portions, each of which 

 constitutes the starting-point of a new individual. 



During recent years the Bacteria have been considered as 

 the cause of various diseases, and in some instances this has 

 been clearly demonstrated, as in the case of splenic fever, 

 caused by Bacillus Anthracis. 



