Sphaerotheca 73 



persistent mycelium in the two forms (on Euphorbia and Ribcs) are 

 morphologically the same ; the on!}' difference I have been able to 

 detect IS that in the form on Euphorbia the hyphae arc perhaps 

 slightly more flexuous, and the perithecia are sometimes more 

 irregularly shaped, with a slightly larger (especial!}' longer) ascus ; 

 but these differences are not, I believe, constant, and at any rate are 

 not more marked than those often found in the forms of one spe- 

 cies on different host plants. On the other hand there is so close 

 a resemblance in the habit and general morphological characters 

 of the two forms that I feel compelled to consider them as belong- 

 ing to one species. It would be extremely interesting if experi- 

 mental work could be carried out to test the correctness of this 

 view that the fungus on American gooseberries and on European 

 spurges belongs to the same species. The plant on Euphorbia is 

 apparently not common in Europe, but where it does occur it 

 should be seen if the conidia are capable of infecting gooseberries ; 

 in America attempts should be made to infect species oi Euphorbia 

 with the conidia of S. viors-uvae on Ribcs, 



I have, In two instances, seen perithecia containing three asci 

 in American specimens of 5. viors-uvae ; the asci were much 

 smaller than usual (about 6ox 35 ,«) and ovate-oblong in shape. 



The record by Berkeley (35) of the occurrence of the present 

 species on " grapes " is due to some error, as in the specimen (now 

 in the Kew Herbarium) to which reference is made, the fungus is 

 growing on the leaves and the berrj- of some species o{ Ribcs. 



In America 5. mors-uvac is common on wild and cultivated 

 species of Ribcs^ and is well known as a widely-spread disease 

 under the name of the "gooseberry-mildew/' As the specific 

 name denotes, the fungus is especially harmful in attacking and 

 destroving the fruit, covering the berries with its persistent felted 

 dark-brown mycelium. It is not, however, confined to the fruit, 

 but often forms large confluent patches on the stems and leaves. 



As a fungicide, Gofif (147) recommends potassium sulphide. 

 The mixture used was one-half or one-fourth of an ounce of the 

 sulphide to a gallon of water, and was applied " as soon as the 

 leaves had begun to expand (May 3), and the application was re- 

 peated after every hard rain until June 24, nine sprayings having 

 been made in all. The new growth, as well as the crop of fruit, 



