NOTES ON RECENT RESEARCH. 



191 



ment of the parasite grow to an abnormal size and shape, and then 

 gradually pass into a state of complete rottenness, rendering their incor- 

 poration with the soil a comparatively easy process. But as each putrid 

 root contains countless numbers of the exceedingly minute resting spores 

 of the disease-producing fungus, the soil bearing a diseased crop soon 

 gets thoroughly infected, rendsring it for the time being entirely unfit for 

 the growth of that or any other Cruciferous crop. 



Numerous experiments, both in this country and abroad, have been 

 tried in order to discover a sure method of prevention of this fatal 

 plant disease, the most recent being those recorded by the Staff' Botanist 

 of the New Jersey Agricultural College,* who has been experimenting 

 with club-root for the last six years. 



Of course all efforts after prevention must be directed towards the soil, 

 as that is the source of all infection to seedling plants. In these series 

 of experiments a considerable number of antiseptic substances were 

 applied in varying proportions to the soil, but, as already discovered by 

 other experimentalists, air- slaked lime is the only certain remedy. The 

 amount used per acre varied from thirty-five to fifty bushels. The 

 experiments also show that time must be given for the quicklime to act, 

 as, if applied to the land in spring just before seeding, less benefit arises 

 than is secured by incorporating it with the soil in autumn. Similar 

 results have been arrived at in this country by Sommerville and others. 

 Kainit had no effect, while copper sulphate injured the crop without 

 harming the parasite in the very least. Corrosive-sublimate- seemed to 

 have some value if used in solution, but proved injurious to the crop when 

 the strength passed a certain standard. Common salt, even at the rate of 

 600 lbs. per acre, had no effect upon either crop or club-root. Strangely 

 enough sulphur, applied at the rate of 300 lbs. to 1,200 lbs. per acre, 

 actually increased the percentage of clubbing. Carbonate of lime, at 

 the rate of 3,000 lbs. an acre, seemed to produce good results in a year's 

 time, but was not nearly so effective as the burnt lime. 



It was observed that irrigation in an infected field greatly increased 

 the virulence of the disease. It may be presumed that the abundance of 

 moisture gave greater facilities for the locomotion of the motile " spores " 

 of the slime-fungus, and so helped to spread the infection. 



A very interesting experiment, although on a small scale, was with 

 Buckwheat in relation to clubbing in Turnips. This plant was sown in 

 an infected plot, and the crop allowed to reach the seeding period. The 

 stems were then chopped up and dug into the soil, and a crop of Turnips 

 sown on the land. A distinct reduction in the percentage of diseased 

 roots was noticed, and even better results were secured the following year ; 

 but after that, the effect of the Buckwheat rapidly ceased, and the soil 

 got " turnip-sick " again. 



It is well known that, so far as present experience goes, no plants 

 outside the Cabbage or Cruciferous family are attacked by this particular 

 kind of disease, and even among Cruciferous plants there are gradations 

 in susceptibility to the attack. The following list is compiled from the 



* " Twentieth Annual Report of the New Jersey State Agricultural Experiment 

 Station," and the " Twelfth Annual Report of the New Jersey Agricultural College 

 Experiment Station for the year 1899." 



