224 



Clover Sickness. 



[JULY, 



an easy matter, and it is often practically impossible to refute 

 the hypothetical predisposition clause so frequently advanced. 



The arrival of an ample supply of clover attacked by " eel- 

 worms " at Kew for investigation, furnished an opportunity 

 for experiment. English red clover was used. 



Experiment i. — The surface of the soil in which a batch of 

 seedlings was growing was sprinkled over with finely cut up 

 clover containing eelworms. At the expiration of two months 

 the stems of the plants were badly infected, and showed the 

 characteristic swollen bases. 



Experiment 2. — Full-grown plants were treated as in Ex- 

 periment No. I. No infection followed. 



Experiment 3. — A layer of finely cut-up infected clover was 

 placed at the bottom of a plant pot and covered with five 

 inches of soil in which seedling clover w r as planted. No infec- 

 tion followed. 



Experiment 4. — The surface of the soil in which a batch 

 of seedlings w r as growing was covered with finely cut up 

 infected clover, this again w T as sprinkled over with crushed 

 sulphate of potash, at the rate of two ounces to the square 

 yard (about 4 cwts. to the acre). No infection followed. 



In a check experiment the plants were supplied with infected 

 clover, but the application of sulphate omitted, the seedlings 

 were infected, proving that in Experiment 4 the eelworms 

 were killed by the sulphate of potash. 



These experiments prove : — 



(1) That eelworms can infect and kill otherwise healthy 



clover. 



(2) That infection can only be effected during the seedling 



or quite young stage of clover. 



(3) In the case of infected land, if the eelworms are burie 



to a depth of 5 in. in the ground, no infection take 

 place. This points to deep ploughing as a remedy. 



(4) If a diseased crop is treated with sulphate of potash, at 



the rate of 4 cwts. per acre, the eelworms are destroyed. 

 Kainit has been recommended as a remedy, but as its sulphate 

 constituent alone is of value for this purpose it w r ould be 

 necessary to apply about ton per acre, and at the prices 

 now quoted kainit would be more expensive than sulphate 

 of potash, and would not be so prompt in its action. 



