516 On a New Clover Disease. 



been destroyed or counterbalanced by cultivation, the plants 

 have become more delicate and liable to adverse influences. This 

 is indeed the condition at the present day of the vine, beet^ 

 rape, lucerne, &c. 



Can man, who causes these evils, do anything to overcome 

 them ? Certainly : either by producing new natural varieties or 

 by destroying the causes of the diseases which are the results of 

 cultivation. But, unhappily, when he attempts to remedy the 

 evils, his method is not practicable, and the means he employs 

 are not successful. Should he then be discouraged, and do 

 nothing ? On the contrary : by renewed patience and persevering 

 research, he must investigate every detail of the cause of the evil 

 until he discovers some efficient remed}'. While waiting for the 

 happy time when science, Avith the help of experience, shall show 

 us how to overcome all these difficulties, I regret that I have to 

 announce a new disease affecting fodder plants. 



Clover, which up to the present time has suffered only from 

 dodder and some insects, has this year been injured in a remark- 

 able manner at Grignon, The clover was sown in 1873, part with 

 blue winter wheat {^Ble hien) and part with rye ; the previous crop 

 was one of potatoes. The soil, a valley diluvium, is very good 

 and has a great depth of vegetable mould. The clover grew 

 well on the field, and at the harvest formed a very regular turf. 

 In the month of February last a considerable portion of the 

 plants withered, blackened, and decayed. Fi'om this time the 

 evil continued, the number of diseased plants daily increased, 

 and with them the empty spaces in the field. The disease was 

 most injurious where the wheat had grown and in the neighbour- 

 hood of potatoes, while only a few plants were attacked where 

 the rye had groAvn. 



The folloAving description is the result of very close observation 

 of the disease : — The diseased stems are not generally contiguous, 

 but are scattered among the healthy ones, sometimes in small 

 groups of from tAvo to six plants. The diseased plants can 

 easily be recognised in Avalking through the field. When the 

 disease attacks a plant the leaA^es speedily begin to fade, as if 

 the root had been cut just below the ground a few hours pre- 

 \aously ; they gradually blacken and then decay. If the plant 

 is pulled up on the first appearance of the disease, the stem in- 

 A"ariably breaks just above the ground. This looks as if the root 

 had been destroyed by a Avorm, a mole-cricket or other insect, or 

 by some kind of larva : but it is not so ; for Avhen the root is care- 

 fully taken out of the ground, it is found to be perfectly healthy, 

 so that the seat of the disease must be looked for on the stem 

 above the ground. 



Nothing can be detected in the blade or stalk of the leaves, or 



