318 



USTILAGINEAE. 



the plant as a whole did not seem to be much affected. On 

 the other hand, a case was observed near Munich where a 

 large plot of violets was completely killed out in a few years 

 by this fungus. 



The anatomical changes induced on Viola odoraia were 

 investigated by Wakker^ with the following results : a swelling 

 of the stems, leaves, and flower-stalks occurred, often accom- 

 panied by considerable twisting and rupture of the epidermis ; 

 these changes were not caused by any enlargement of cells, but 



Fig. 174. — UrocystU violae on Viola. Smiit-pustules are present on leaf .stalks 

 and fruit-stalks, accompanied by malformation, (v. Tubeuf phot) 



the cambium remained longer active in the stem, and a secondary 

 division of rind-parenchyma or mesophyll could be observed, 

 along with a disappearance of intercellular spaces ; accessory 

 vascular bundles were formed, but the secondary vessels remained 

 incompletely developed. In short, new growth occurred, not 

 in the earlier stages of the host's life, but in the adult. 

 Especially noteworthy is the formation of a small-celled tissue 

 resulting from cell-division in the rind-parenchyma and the 

 mesophyll ; this serves as a nutritive tissue for the fungus, 



1 Wakker, Pringsheim's Jahrbttch, 1892. 



