PLOWKIGHTIA. 



231 



Plowrightia morbosa (Sch.) (Britain and U.S. America). 

 Black-knot of the plum tree.^ In America thi.s is a very 



Fio. 115. — Ploirriiihtia mor- 

 hosa. Ascus, with eight 

 spores. Spores in germinn- 

 tion. Filuinentou.s jwira- 

 physes. (Cop. fnmi F!\rlo\v.) 



Fig. 114. — Plowrightia morbosa. (v. Tubeuf phot.) 



injurious and widely distributed disease of various species of 

 Prunas, especially plum and cherry. The living branches and 

 twigs become coated with a crust of warty excrescences, and 

 at the same time are more or less thickened and deformed. 

 A mycelium permeates the tissues of those swollen twigs, and 

 forms black crusty stromata in which the perithecia are 

 embedded. The perithecia contain simple paraphyses and eight- 

 spored asci. The spores consist of a larger and a mucli smalk-r 

 cell. (Pycno-conidia arc produced frequently in artificial culture, 



1 Fallow, Bulletin Bussey Institution, Part v., 1876. 

 Humphrey, Animal Report of Mans. Exper. Station, ISOO. 

 Lodeman (Cornell Uvii: Exper. Station. Bulletin No. 81, 1894) giv.-s 

 general account of Black-knot and a Bibliography. 



