190 



The spread of the disease in the early spring is evident from an obser- 

 vation of an infected plant. A single plant often has at first only one or 

 two infected spots. As the new leaves develop they are seen to be free 

 from the disease, but a few days after a damp period these leaves are 

 badly infected. This disease is, in many respects, an early spring one, for 

 the most luxurious growth of tbis species of violet is during April and 

 May and the fungus seems to thrive best during cold, damp weather. At 

 no time do tbe number of spots become so great as to kill the leaf. The 

 damage done by this fungus is evidently negligible so far as this species is 

 concerned. 



The fungus spores are probably distributed tbrough the usual agents. 

 They are produced in great numbers on both sides of the leaf and they 

 germinate readily in tap or rain water. 



Artificial Inoculations. — A detailed report of the experiments on inoc- 

 ulations made would be out of place at this time. Summarizing these, it 

 was found that infection by sprayed spores on the leaves was readily 

 brought about if the plants were kept very moist for several days. The 

 number of infections were small on each plant. Cross-inoculations on 

 V. puoescens and V. striata gave negative results. 



Cultural Characters. — The fungus is easily isolated by poured plates 

 of the spores. Cultures were made on various media, but a description of 

 the development on dextrose-potato agar will be sufficient to show the gen- 

 eral character of the growth. The mycelium is at first hyaline, mostly 

 confined to a thick growth on tbe surface of the agar, with scanty aerial 

 mycelium. At the edge of the advancing mycelium the agar takes on a 

 pink and then a red color which is very striking. Later the mycelium dark- 

 ens and in some cases within four days conidia are to be found. The dark- 

 ening of the mycelium continues and within two weeks a heavy, black, 

 stroma-like crust is formed over the surface of the agar. On this stroma 

 byaline, gelatinous areas of conidia are developed. 



Conclusion. — This preliminary report on a leaf spot of Viola cucullata 

 is given in order to stimulate others to examine the plants of this species 

 during the coming spring, thus establishing more definitely its range and 

 determining whether or not it is confined to this one host. An effort will be 

 made by the writer to determine the relationship of this species to the one 

 occurring on Trillium and on V. rotund if olia. 



