1893.] • PUBLIC DOCUMENT — No. 33. 227 



This parasite is very destructive under jfjivorable condi- 

 tions, but tliere is no reason to doubt tliat thorough and 

 timely spraying will control it, at least where the host-plants 

 are otherwise in a condition to make health v orowth. 



4. Damping Off. — Pijthium DeBaryanum Hesse. 

 Seeding plants of many species have long been known to 

 be destroyed in great numbers by the affection known as 

 " damping off." To the number of those known to l)e thus 

 affected was added in a previous report* the cucumber plant, 

 and the cause of the trouble was shown to l)e the same 

 fungus to which it is commonly due in Europe. The same 

 fungus has repeatedly been met with in the cucumber house 

 during the past two years, and has caused much loss of time 

 and of plants. Last fall seedlings which had started well in 

 a bed of fresh, rich soil, just taken from a compost heap 

 where it had lain for at least two years, were so generally 

 attacked that nearly all were lost. The attacks were so 

 nearly sinmltaneous that there can be no doul)t that the 

 fungus was generally diffused throughout the soil ; and, 

 unless it is able to propagate itself in some way of which 

 we now know nothing, the spores from which the infection 

 originated must have remained alive in the compost for a 

 long time. Unfortunately, no practicable treatment can be 

 recommended beyond the removal of affected seedlings, 

 with the surrounding soil, as quickly as possible after they 

 show the presence of the fungus. 



5. The Leaf Blight. — Cladosporium ciicumerinum Ell. & Arth. 



(Plate IV ) 



Early in October we received from Messrs. C. H. Chase 

 & Son of Clinton some cucumber plants whose stems and 

 roots were quite healthy, while the leaves were badly wilted, 

 and had a peculiar watery appearance. Everything indi- 

 cated that here was a definite disease, as leaves on a given 

 plant showed various stages in its progress, those in the 

 latest stages being reduced to a mass of decaying tissue, 

 while those in the earliest stages were just beginning to 

 wilt and to show translucent watery spots. The senders 



* Eighth Report Massachusetts Experiment Station, p. 220, and Pi. II. " 



