PROTOBASIDIOMYCETES 407 



given, and requisite irrigation is desirable when there is a tend- 

 ency for drying out to affect the health of the plant during the 

 summer. It would appear, however, that the best method of con- 

 trolling the fungus is by the selection of resistant sorts. Since the 

 Palmetto variety has shown itself fairly resistant in the East, it is 

 probable that other sorts may be obtained which will possess some 

 of the desirable qualities of the Conover, with the resistance of 

 the Palmetto. So far as I am aware, no extensive report has 

 been made upon the resistance of European varieties under our 

 conditions. 



XI. VIOLET RUST 



Puccinia Viola (Schum.) De C. 



Arthur, J. C, and Holway, E. W. D. Violet Rusts of North America. 

 Minn. Bot. Studies Built. (Ser.) 2 : 631-641. 1901. 



This species of violet rust is parasitic on about sixty different 

 hosts in the genus Viola throughout North America and parts of 

 South America, also Europe and Asia. The spermogonia and 

 jecidia occur early in the season in light brown spots scattered 

 over leaves and stalks. The ascidiospores are ovoidal, 16-24 X 

 10-18/u. The uredospores and teleutospores follow in succession, 

 both of these on the under surfaces of the leaves, producing no 

 definite spots ; yet a large number of sori may become confluent 

 so as to present the appearance of dark brown areas. The fungus 

 is not of much consequence from an economic point of view in 

 relation to violet culture, but it is, nevertheless, the most common 

 of the five (assuming the validity of some species) violet rusts. 



XII. MINT RUST 



Puccinia Mentha Pers. 



This is a species apparently well distributed throughout a large 

 part of the world on about thirty-five members of the mint family. 

 The fungus is closely related to a number of other species whose 

 host plants are also certain mints. In fact, more than thirty species 

 of rusts have been described upon the various mints, and the studies 

 that have thus far been made upon these indicate an interesting 

 evolution of the parasitic forms. The species referred to, however, 



