1893.] PUBLIC DOCUMENT— No. 33. 229 



germinating and infecting fresh tissues. Unfortunately, I 

 bad no suital)le plants for infection at the time the material 

 was received ; but a careful study of the various stages of the 

 disease presented by the different leaves of a plant affords 

 little room for doubt that this funi^us form is its efficient 

 cause. 



The only mention of a disease of this host caused by a 

 similar fungus that has come to notice is that by Arthur,* 

 who has described the development of decayed spots on 

 cucumber fruits, observed by him in New York and Indiana. 

 In this case the cause of the decay, Avhich was a source of 

 umch loss, appeared to be a Cladosporium form, which the 

 writer called Cladosporhmi cucujnerininn Ell. & Arth. It 

 is impossible to say that our leaf-destroying form is the 

 same as this which attacks the fruits, but there is no reason 

 for assuming them to be diff'erent. On the other hand, it is 

 by no means certain that either the leaf or the fruit form is 

 distinct from forms previously known on other hosts. In- 

 deed, the accumulation of evidence that the common fin-m 

 known as Clad, herbarum, until very recently regarded as 

 only saprophytic, is capable of actively parasitic life, must 

 weaken one's doubt that most of the related forms possess 

 the same capacity. Our knowledge of the Cladosjjorium 

 forms is very fragmentary, and there can be no doubt that a 

 thorough study, based on detailed cultures of the various 

 forms, would result in a great reduction in the number of 

 so-called species. For the present, then, our parasite may 

 bear the name given by Ellis and Arthur, in the sense that 

 it is a Cladosporium, attacking cucumber plants, without 

 any necessary implication as to its real distinctness from 

 forms attacking other host-plants. 



It seems altogether probable that prompt spraying as soon 

 as this disease begins to appear will prevent its spread to 

 healthy plants. But, in view of its rapid progress, a very 

 little delay may be fatal. 



* Sixth Report New York Experiment Station, p. 316, 1888 ; and Nineteenth Bull, 

 Indiana Station, 1889. 



