272 TIMBER AND SOME OF ITS DISEASES [CH. xili. 



to " rot off/' A large class of diseases of this kind is 

 only too familiar, in its effects, to cultivators in all 

 parts of the world. Every gardener probably knows 

 how crowded seedlings suffer, especially if kept a trifle 

 too damp or too shaded, and I have a distinct recollec- 

 tion of the havoc caused by the *' damping off" of 

 young and valuable Cinchona seedlings in Ceylon. 



In the vast majority of the cases examined, the 

 " damping off" of seedlings is due to the ravages of 

 fungi belonging to several genera of the same family 

 as *"he one {Pkytophtkora infestans) which causes 

 the dreaded potato disease — i.e, to the family of 

 the Peronospore^ — and since the particular species 

 {Pkytophtkora omnivord) which causes the wholesale 

 destruction of the seedlings of the beech is widely 

 distributed, and brings disaster to many other plants ; 

 and since, moreover, it has been thoroughly examined 

 by various observers, including De Bary, Hartig, 

 Cohn, and others, I propose to describe it as a type 

 of the similar forms scattered all over the world. 



It should be premised that, when speaking of this 

 disease, it is not intended to include those cases of 

 literal damping off caused by stagnant water in ill- 

 drained seed-beds, or those cases where insufficient 

 light causes the long-drawn, pale seedlings to perish 

 from want of those nutrient substances which it can 



