112 



FUNGI AND FUNGICIDES 



tissues, which the fungus under consideration first 

 produees. 



Treatment. The burning of fallen catalpa leaves 

 in autumn is ;m advisable preventive measure. Proba- 

 bly early sprayings with Bordeaux mixture, or some sim- 

 ilar fungicide, would prove an effectual remedy. 



The only important article on this subject that has 

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



FIG. 51. CATALl'A I.EAK-SI'OT. 

 a, Section showing spore pi'oduction ; 6, spores; c, spores germinating. Magnified. 



of the United States Department of Agriculture for 

 188? (pp. 364-366). 



The Cotton wood Leaf = rust 



Melampsora 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 proper 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. Eaking 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 



