DEVELOPMENT OF PLANTS 



155 



simple in structure are the bacteria that the real nature of the 

 plant body is somewhat a matter of dispute. The plants are 

 unicellular and surrounded by a delicate thin wall which in- 

 closes a colorless and slightly granular protoplasm (Fig. 91, 

 A, i). There is no nucleus comparable to that of the higher 



Fig. 91. Forms of Bacteria: A, Bacillus suhtilis, a form common in hay 

 infusions, i, motile state; 2, cells with spores; 3, slimy mass of bacteria, 

 the zooglea condition, that appears on the surface of infusions, cooked veg- 

 etables, etc. B, Spirillum. C, a coccus form that appears in pus. D, mobile 

 and spore stage of lock-jaw bacillus. 



plants, although indications of it are seen in a few scattered chro- 

 matin grains. The cell content is very simple and totally lacking 

 in plastids and other differentiations with which you are familiar. 

 The slimy appearance of bacteria noticeable where they grow 

 together in colonies is due to the mucilaginous excretion from 

 their bodies which is often brightly colored. Bacteria range 

 from globular to rod-like and curved forms (Fig. 91). Many 

 are motile by means of cilia, as in the case of the zoospores of 

 the Myxomycetes, which project singly or in tufts from the ends 

 of the cells or in varying numbers from all sides. 



(a) Reproduction of Bacteria. — ^This is a simpler process than 

 in the slime moulds and much more rapidly effected when the 

 conditions are favorable for growth. This process consists of 



