

62 BOTANICAL GAZETTE [july 



invading cells. Sometimes a fusion of a number of these invading 

 cells, preparatory to the formation of a larger Plasmodium and the 

 breaking down of the separating host cell walls, may be noted. All 

 these features are illustrated in fig. 7. 



The discussion of the studies upon the life history of the para- 

 sitic organism may be concluded by a brief reference to the subject 

 of nuclear divisions in the different stages. Had division figures 

 not been found, identification of the nuclei in the plasmodium 

 would have been questionable, since these nuclei are very small 

 and details of their structure are not easily distinguished. Divi- 

 sion figures , however, are very common in some of the prepara- 





clear and refractive. Just how the formation of the spores takes 

 place has not been determined. 



Around the margins of the larger cavities containing spores the 

 naked protoplasm of the plasmodium may be found in a more or 

 less shrunken condition. The similarity of this protoplasm to 

 that within the spores is convincing evidence of the origin of the 

 spores from the plasmodium, the most noticeable difference being 

 in the more regular arrangement of the nuclei within the spores. 

 Isolated host cells or groups of cells may be occupied individually 

 by separate plasmodia; it would seem that these small plasmodia 

 may develop walls about themselves and become resting spores. 

 The subject of spore formation is in need of very careful and pro- 

 longed investigation. 



Primary infection, the actual entrance of the parasite into an 

 uninfected host, has not yet been observed. The fact that the 

 parts invaded are the adventitious buds and the secondary roots 

 in the very earliest stages of development minimizes the chances 

 of such an observation. There is little doubt, however, that 

 either the zoospores before fusion, the zygotes, or the plasmodia 

 formed on the surface of the host may penetrate the embryonic 

 host tissues. In young bud galls cases have been found in which 

 practically every cell of the growing tip was occupied by the para- 

 site (fig. 7). From this figure it will be seen that the infecting 

 cells of the parasite vary greatly in form and size after penetration. 



* 



Often they are found in contact with the host nucleus, the latter 

 being still intact. Sometimes a host cell contains several of the 





