BY R. GREIG-SMITH. 299 



seen (figs. 8, 10). Occasionally a single pole is noted (fig. 12). 

 The spherules are sometimes flattened and present the appearance 

 of a bipolar rod or bacillus (shown double in fig.9).* Since the 

 Rhizobium cell is a tubular capsule containing spherules, it is 

 easy to understand that by an increase in the number of these 

 spherules the cell may become misshapen, and irregular forms be 

 produced. The beginning of a T shape is depicted, and also an 

 exclamation mark, "!" (fig. 10). The displacement of the 

 spherules from internal pressure is often seen (fig. 11). The poles 

 have no definite inclination to the direction of the rod-shaped 

 capsule: sometimes they are parallel, at others they are at right 

 angles, while, again, they may be at a smaller angle (fig.7). 

 Since the poles of the spherules have inclinations at different 

 angles to the length of the tubular rod, they will, upon dividing, 

 grow in different directions. Should the growth proceed at a 

 pronounced angle to the rod, an irregular form or bacteroid will 

 result. The same will occur if the spherules within the rods 

 increase in size at different rates as in fig. 6. A flattened 

 terminal structure may be seen at an angle to the rod (fig. 13). 



Such are the most instructive forms that were seen in a culture 

 of a Robinia race. Those shown in figs. 7 and 12 were by far the 

 most numerous; occasionally long and much branched forms were 

 seen, the whole contents consisting of the swollen spherules. 



A Bean race which was also examined showed a similar 

 structure (Plate xxi.) of the cells, but as they chanced to be much 

 more swollen and more branched forms were present, the films 

 were very instructive. Probably on account of the very swollen 

 condition of the spherules, the bipolar staining was not so much 

 in evidence. Although the majority of the cells were rod-shaped,. 

 as in the Robinia slime, the odd forms showed points of interest; 

 A curious, but not uncommon, massing of the spherules is shown 

 in fig. 3, in which the alteration of shape due to pressure is seen. 



* The bipolar rod-shape recalls the form of the bipolar staining bacteria 

 such as Bact. pestis, which, under some conditions, exhibits a branching 

 formation. 



