STUDIES ON CLUBROOT OF CRUCIFEROUS PLANTS 443 



Furthermore, amxba-like bodies are found in the epidermal cells or the 

 layer next to them, which also look very much like Plasmodiophora 

 but seem to be inclosed in a delicate wall. Stages have been found in which 

 each of these bodies has an appendage, or neck, which protrudes thru 

 the outer epidermal cell wall (fig. 109, B, c). The organism compares very 

 closely with that described by Woronin (1878) as Synchytrium Brassicae 

 and later by Dangeard (1886) as Olpidium Brassicae. Positive proof of 

 its identity is lacking. 



The chytrid never produces any hypertrophy or other outside symptoms 

 by which a diseased plant can be recognized, so that specimens were 

 found only accidentally. For this reason it was impossible to study 

 the swarm-spore stage or the details of the life history of the organism. 



The organism evidently enters by way of the root hairs, and never 

 penetrates far into the host. None of the invaded cells are changed in 

 size or general appearance. Even the invaded root hair does not have 

 that slight enlargement which has been mentioned in connection with 

 the entrance of the uninucleate amoeba of Plasmodiophora Brassicae. 



The fungus can infect a plant that seems perfectly healthy. 'At least 

 it is not a saprophytic form following the clubroot organism, as roots 

 were sectioned which showed it alone. 



BACTERIA IN RELATION TO PLASMODIOPHORA BRASSICAE 



Pinoy's (1902, 1903, 1905, 1907) work with Myxomycetes in their 

 relation to bacteria, and his subsequent suggestion that there is a true 

 symbiosis between the two, represent a very interesting phase in the study 

 of Plasmodiophora. It has long been held that certain saprophytic slime 

 molds feed on accompanying organisms, and the data at hand seem entirely 

 plausible. Lister (1894) has seen the ingestion of bacteria by active 

 swarm-spores. The experiments of Vuillemin (1903), Nadson (1901), 

 and Potts (1902) show that Dictyostelium mucoroides Bref. feeds directly 

 on bacterial colonies and destroys a large number of these at fruiting 

 time. 



The general conditions of subsistence governing saprophytic forms 

 and those controlling parasitic organisms are not the same, however; 

 so that from a priori reasoning it would seem justifiable to say that Plas- 

 ,;iodiophora Brassicae needs no concomitant organism in its life cycle. 

 Yet the case is not so clear, since, on examination of nearly every root 

 that has been diseased for some time, such an organism is found to be 

 present. When the surface of these roots is sterilized and placed in agar, 

 they may show no indication of bacteria until they are cut in two and 

 the fresh surface is placed in contact with the medium. Moreover, E. F. 



