FEBONOSFOBA PARASITICA ON" CAULIFLOWER. 123 



sulphur powder, and repeating this treatment several times 

 after transplanting to the field. Marchal, on the advice of 

 Cornu, recommended spreading sawdust saturated with 

 copper sulphate around the plants as a mulch. He states 

 that where this was used, the disease was practically 

 stopped. 



In the case of plants affected by the Peronospora at the 

 Garden, a number of sprays were used including copper 

 sulphate, copper ammonium carbonate, and potassium sul- 

 phide. In order to make these solutions stick totheleaves 

 small quantities of glue were added, and it was found that 

 this formed a very effective way of holding the solutions 

 on the leaves of the cauliflower. Good results were ob- 

 tained with all of these sprays, with the exception of cop- 

 per ammonium carbonate, which, while it killed the fungus, 

 induced the formation of an enormous number of oedemata, 

 on the lower surface of the leaves in particular. This will 

 form the subject of another paper. The fungus disap- 

 peared during the spring months. The following winter the 

 beds of this greenhouse were carefully treated with lime, 

 and since that time there has been no further attack of the 

 cauliflower in these houses. 



It is of interest to note the very local and sporadic 

 appearance of the Peronospora parasitica in this instance. 

 Although careful search was made for it in other green- 

 houses of this vicinity, this was practical^ the only case 

 where it occurred. Inquiries made in other parts of the 

 United States, at the time, failed to show its occurrence on 

 cauliflower at other points. This is rather striking because 

 the fungus itself is a common one on the native wild plants 

 in most parts of the United States, and it might be 

 expected that it would show itself on cultivated cruciferous 

 plants more frequently than it does. The possible explana- 

 tion may lie in the fact that there are certain physiological 

 strains on different species of cruciferous plants, similar 



