Chrysanthemum Diseases 237 



Piloholus crystallinus. The spore-bearing stalks of 

 this fungus are possessed with a mechanism which 

 throws off the ripe spores considerable distances. 

 Being covered with a sticky substance, these spore 

 masses readily adhere to anything standing in the 

 way. The specking may be expected wherever 

 manure is used as a mulch. According to Craig* 

 the trouble may be promptly stopped by a light ap- 

 plication of air-slaked lime. 



Rust 



Caused by Puccinia chrysanthemi Rozc. 



Symptoms, Rust may be readily distinguished 

 from all other diseases of the chrysanthemums. It 

 appears as tiny, rusty blisters the size of a pinhead. 

 When several appear together the blister assumes 

 a larger size (fig. 50, c). At first, the blister is 

 covered by the epidermis of the leaf. With age, 

 however, the epidermis bursts and breaks away, ex- 

 posing a brown powder which is made up of mil- 

 lions of spores of the rust fungus. On badly in- 

 fected plants, the leaves may be all covered with 

 the rust sori which nearly always appear on the 

 underside of the leaf. It was previously believed 

 that the rust of chrysanthemum was the same which 

 attacks common weeds belonging to the same com- 

 positse family as the chrysanthemum. However, the 

 investigations of Arthur t have definitely shown that 



♦Craig, J., Canada Expt. Farms Repts., 1897: 91-133, 1898. 

 t Arthur, J. C, Indiana Agr. Expt. Sta. Bui. 85: 143-150, 1900. 



