286 



THE FUNGI WHICH CAUSE PLANT DISEASE 



attacking first the parenchyma cells and medullary rays. The 

 young stromata appear under the bark bearing when young small 

 unicellular conidia. The stromata later turn hard and black and 



Fias. 213-214. — N. discreta, B, stroma and perithecia, C, a 

 perithecium, D. asci and spores. After Hasselbring. 



in the upper layers bear numerous fiask-shaped perithecia with 

 long necks, Figs. 213-214. 



Ustulina Tulasne (p. 285) 



Stroma superficial, subeffuse, rather thick, determinate, at first 

 clothed with a pulverulent cinereous conidial hymenium, finally 

 rigid, carbonous, black, bare and generally more or less hollow; 



