208 THE FUNGI WHICH CAUSE PLANT DISEASE 



P. ruba (Pers.) D. C. causes reddish spots on the leaves of 

 Prunus. Stroma at first bearing pycnidia 

 (Libertella rubra) with filiform hooked, con- 

 tinuous conidia. Perithecia produced on old 

 leaves, bearing ellipsoid to elongate asci; 

 spores 10-13 x 6 m, smooth. 



The invaded leaf 'tissue is colored by the 

 mycelium which bears a reddish oil. Nu- 

 merous perithecia are immersed in the 

 diseased area and, opening to the surface, 

 extrude spores which seem incapable of in- 

 fecting. During winter the stroma darkens, 

 " turns hard and produces the perithecia and 



^D, asd; E, TOnMk.' ascosporcs. Ascogouium and trichogyne-like 



After Fisch. ^^^^^ ^^^^ ^^^^ described."^ 



p. ochraceum (Wahl.) Sacc. occurs on Prunus padus. 



# 



Valsonectria Spegazzini (p. 198) 



Stroma thin, cushion-shaped, under the bark of the host; peri- 

 thecia similar to those of Valsa, sunken in the stroma, the beak 

 erumpent, red; asci cylindric, 8- 

 spored; spores 2-celled, hyaline or 

 light brown. 



A genus of but three species which 

 differ from Valsa chiefly in their % 

 red color. ' &" 



V. parasitica (Murr.) Rehm.'^^- ™' .^ 



Pustules numerous, erumpent, at '" — ~» .A^"-^^. 



first yellow, changing to brown at ^^a. 149.— Showing a pycnidTum of 



maturity; perithecia usually ten to Valsonectria and the manner iu 

 ■' ' ^ •' which the spores issue from it. 



twenty in number, closely clustered, After Murriii. 

 flask-shaped, deeply embedded in the stroma in the iimer bark, 

 scarcely visible to the unaided eye; necks long, slender, curved, 

 with thick black walls and rather prominent ostiola; asci oblong- 

 clavate, 45-50 x 9 m, 8-spored; spores usually biseriate, hyaline, 

 oblong, rounded at the ends, often slightly constricted, unisep- 

 tate, 9-10 X 4-5 /i. Summer spores very minute, 1 x 2-3 n, pale- 



