434 



BULLETIN 387 



has not yet begun (fig. 102, D). On the other hand, it would seem that the 

 fusion of two swarm-spores would give an increase in size, but the measure- 

 ments of amoebae just after penetration show them to be no larger than 

 the swarm-spores just out of the spore wall. Consequently Winge's theory 



FlG. 102. SPOKES AND AMCEB^E OF FLASMODIOPHORA BRASSICAE 



A, Spores before their final separation from one another; B, cell filled with amoebae; C, cell filled with 

 spores. All X 800. D, Formation of spores, X Soo 



must be discarded. It thus appears that the real fusion stage, if there is 

 one, is still to be discovered. 



DISTRIBUTION WITHIN THE HOST TISSUES 



As stated above, the uninucleate amoeba, just after its entrance into the 

 host, lies at first in a small cavity produced by the outward swelling of 

 the part of the root hair at the point where the organism entered. This 

 protuberance is no doubt caused by the irritating presence of the para- 

 site (fig. 10 1, A, B, E). Following penetration the amoeba increases in size 

 and pushes toward the center of the hair. The movement is accomplished 

 by an actual amoeboid creeping, and an elongation and gradual segmen- 

 tation of the forward part. Woronin (1878) was able to observe the 



