218 



THE FUNGI WHICH CAUSE PLANT DISEASE 



Some twenty species are known. They are distinguished from 

 Dothidia by the hyaline spores. 



Fio. 155.— P. morbosa. b. magnified section of a knot showing the 

 penthecia; c, conidiophores and conidia; d. section of a peri- 

 thecmm showing numerous asci, one of which is shown more highly 

 magnified at «,■ /several of the two-celled ascospores germinating 

 m water. After Longyear. 



P. morbosa (Schw.) Sacc.'^="i^"' =•>« 



Stromata elongate, cushion-shaped, rarely tubercular, up to 2 or 



