402 FUNGOUS DISEASES OF PLANTS 



in order to determine the possibility of spreading the disease 

 to vigorous adult plants. Observation would indicate that adult 

 plants may be affected, and consequently that the disease may be 

 spread rapidly during the growing season. In fact, it is only upon 

 this basis that the rapid spread of the fungus can be accounted 

 for. Yet there is very little experimental data upon which to rely 

 for confirmation of this statement. 



Control. Three methods of control have been considered and, 

 when necessary, practiced, and these in addition to a maintenance 

 of the best general conditions of the environment with respect to 

 sanitation. In the first place, resistant varieties should be grown 

 as far as possible. Secondly, it is desirable, where the rust 

 abounds, or where rust-susceptible varieties must be grown, to 

 have simple V-shaped wire mesh supports placed between the rows 

 in order to hold the foliage away from the moist soil, and also to 

 permit of watering without constant wetting of the leaf surfaces. 

 Thirdly, it may be necessary to employ fungicides when other 

 methods fail. In such cases the plants may be sprayed once each 

 week with a solution of copper sulfate about 1-500 (1 lb. copper 

 sulfate to 12—15 gallons of water), or with a solution of potassium 

 sulfide 1 ounce to 1 gallon. 



IX. UROMYCES: OTHER SPECIES 



Uromyces scutellatus (Schr.) Wint. apparently occurs as a very 

 common parasite of a large number of species of Euphorbia. The 

 species is ordinarily broken up into different forms, which vary very 

 slightly one from another in general appearance and considerably 

 in extreme size, the uredospores being 17—35 * T 4 — 2 3f JL i an d the 

 teleutospores 20-38 X 16-25 fx. Whether this fungus is, in any of 

 its forms, a euheterouredo, or invariably a hemiuredo, as it appears 

 to be, is not definitely determined. 



Uromyces Rumicis (Schum) Wint. This species is found on 

 many members of the genus Rumex. It appears to be a 

 hemiuredo. 



Uromyces Solidaginis (Somm.) Niessl. This is commonly con- 

 sidered to be a microuredo and occurs upon several species of 

 Solidago. 



