196 BOTANY 



take up stain with much avidity. The central body is, however, 

 most readily observed in cells ten days old, and bears some relation 

 to the condition of the cell with regard to the process of division 

 to be described below. It is homogeneous in nature, and more or 

 less spherical in form, in cells which have recently been produced 

 by division, but in some cells, apparently at the same stage, the 

 body presents the appearance of a four-lobed or " tetrad-struc- 

 ture." Owing to the minute size of this body, the existence of 

 such a " tetrad " is very largely conjectural. 



While division of the cells is in progress, the central body 



Fig. 73. — Diagrammatic representation of hypothetical alternative 

 division-cycles in the vegetative cell of Bacterium malvacearum. 

 (After Stoughton, Proc. Roy. Soc. (Lond.).) 



becomes dumb-bell shaped and is comprised of two rounded 

 bodies ; one in each of the daughter cells with a connecting strand 

 between. In other cells, each end of the dumb-bell shaped figure 

 appears to be more or less bilobed or double. In some of the 

 cells this structure appears to be much elongated, and shows only 

 small signs of a dumb-bell shape. This latter phenomenon is 

 usually associated with elongation of the cell as a whole, such as 

 is commonly the case when transverse fission takes place. On the 

 other hand, in some cells, the central structure appears to have 

 completely divided into two portions before much elongation of 



