112 



FUis'GI AXD FUNGICIDES 



tissues, which the fungus under consideration first 

 produces. 



Treatment. — The burning of fallen catalpa leaves 

 in autumn is an advisable preventive measure. Proba- 

 bly early spravings with Bordeaux mixture, or some sim- 

 ilar fungicide, would i3rove an effectual remedy. 



The only important article on this subject that has 

 come to the writer's notice may be found in the report 





'^^^rinM^^L-^J 



a c 



FIG. 51. ( ATALI'A LEAF-SPOT. 



o, Section showing spore production ; 6, spores; c, spores germinating. Magnified. 



of the United States Department of Agriculture for 

 188? (pp. 36-4-366). 



The Cottonwood Leaf = rust 



Melamjysora populina 



The leaves of poplars and cottonwoods are quite 

 commonly covered on the underside with an orange col- 

 ored powder, which consists of the spores of a rust fun- 

 gus. Such leaves usually fall prematurely, so that the 

 trees may be defoliated long before the proj^er time. 

 Later in the season the orange powder is replaced on the 

 leaf by reddish brown, waxy pustules. This is the win- 

 ter stage of the fungus. Raking and burning fallen 

 leaves is advised, as a remedial measure. This fungus 

 is discussed in the 1888 Report of the Department of 

 Agriculture (pp. 390-392). Recent experiments have 



