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formation which takes place in the root system of an attacked plant, a 

 malformation which varies with the kind of plant and extent of the dis- 

 ease, but generally shows as a finger-like swelling of the branch- 

 roots. The first infection probably occurs by a "Zoospore" such as we 

 have described entering a cell of the plant by a root-hairi Inside the host- 

 cell a plasmoddum is formed, the cell is stimulated to rapid Qivision,each 

 nevt^ cell containing a portion of plasmodium.. By this rapid growth of the 

 tissue a swelling results, the cells of which are infected by the parasite. 

 Only the roots are attacked, but as a natural consequence the ability of 

 the plant to absorb water from, the soil is reduced and "v/ilting" ensues, 

 this being usually the first symptom of disease observed. If badly attacked 

 the plant does not develop properl} but remains stunted, and finally the 

 roots decay into an offensively smelling putrid mass. In the meantime the 

 Plasmodium inside the infested cells has undergone spore-forma- 

 tion, such cells under the microscope being seen to be packed full of my- 

 riads of exceedingly small spherical spores. When the roots decay these 

 spores are set free into the soil and by the various tillage operations be- 

 come distributed through the land. Each in course of time will, if condi- 

 tions be favourable, germinate and produce a new infection. Even after 

 the lapse of several years soil infected with spores will still produce dis- 

 eased plants, although it is not quite clear in what form the parasite 

 exists during this time. The disease i very bad in the Maritime Provinces, 

 a.ndl also occurs elsewhere in this country and may be looked for especial- 

 ly in the market gardening areas near large towns. In the United States 

 it is particularly serious in such localities e.g. in the vicinity of Buffalo 

 and New York City.. 



Among cultivated plants the following are known to be attacked: — 

 cabbage, turnips, swede, Kohl-rabi, cauliflower, Brussels-sprouts, rape, 

 radish and white mustard; and am.ongst weeds, charlock, ball mustard, 

 penny cress, worm-seed, mustard, false flax, tumbling mustard, shep- 

 herdl's purse, hare's ear mustard, andi others. 



Control. Although it has, been stated above that no part of the 

 plant except the root is attacked yet there is evidence to show^ that the 

 disease can be spread on the seed. It will be easily realized that if the 

 soil is full of spores, these may be carried to the seed pods in the dust 

 raised in cultivation and blown by wind and some may be m.ixed with 

 the seed in the process of threshing. Hence if it is not possible to secure 

 seed from a locality known to be free from the disease it is advisable to 

 disinfect it by soaking it for 15 minutes in a solution of one part by 

 \veight of corrosive sublimate in 1000 of water. Besides killing the spores 

 of this disease, this treatment is effective against the germs of certain 

 other diseases and does not injure the germination of the seed. 



If diseased roots are fed to stock the spores are liable to escape in- 

 jury from the digestive juices and to pass out into the manure with undi- 

 minished pow^er of producing infection, and such manure would become a 

 most effective means of spreading the disease. It is therefore highly advis- 



