Fungus Diseases of Violets 



465 



strain which became susceptible to the attack of the parasite. 

 We do not know if it has been recorded for Great Britain ; 

 apparently it is closely allied to the preceding species. It is 

 described in detail in the twenty-third Bulletin of the Department 

 of Agriculture, U.S.A. (1900). 



VIOLET-MOULD. 



Peronospora viola, De Bary, causes a dense pale violet-grey 

 mat on the under surface of the leaves of the common Hearts- 

 ease (Viola tricolor), and those of the cultivated Neapolitan 

 violet. It is most abundant in damp weather. The oospores 

 are formed late in Autumn in the dying leaves and parts of 

 the host. 



It is said that no liquid fungicides have been proved to be 

 beneficial, the potassium sulphide spray (water i\ gallons, 

 potassium sulphide 1 oz.), being the best. Plenty of air and 

 little water checks the spread of the disease. 



Does Peronospora viola occur on pansies ? These plants 

 being cultivated forms of Viola tricolor, it is curious if they 

 have resisted the attacks of fungi. There may be fungus 

 diseases of the pansy on record, but there is no mention of 

 such in Massee's " Text Book of Plant Diseases." 



The following diseases of our native wild violets are 

 recorded in Dr. Plowright's " British Uredineae and 

 Ustilaginese." 



Puccinia fergiissoni on Viola palustris. Sori crowded in orbi- 

 cular clusters, forming yellowish or pale spots. (Scotland 

 and Wales). 



Puccinia cegra on V. lutea, var amczna, and V. cornuta; forming 

 scattered, pseudoperidia, with torn, white, partially recurved 

 margins. 



Puccinia viola on V. canina, odorata, tricolor, hirta and sylvatica. 

 Very common from May to October. The iEcidiospores 

 cause yellowish-white patches on the leaves and stems, often 

 distorting the latter very much. The sori of the teleutospores 

 are black, round and small. Does it ever occur on cultivated 

 violets ? 



