DERMATEACEAE 253 



Among the Drepanapezizoideae are the several species of 

 Coccomvces that cause shot-hole diseases of Prunus. These in- 

 clude C. hievialis on cherries, especially Pnimis cerasits, P. aviiirn^ 

 and P. pennsylvaiiica, C. pninophorae on plums, especially P. 

 doinestica and F. americana, and C. lutescens on chokecherry, P. 

 virg'miana, and on black cherry, P. serotina. These species were 

 described by Higgins (1914) and were assigned by Nannfeldt 

 (1932) to the new Genus Higginsia. Their conidial stage is 

 Cylindrosporium. Higgins (1914) established that spermatia are 

 formed in late summer within conidial acervuli and among the 

 conidia. At the same time, within the stromata beneath the 

 spermatiferous layer, archicarps are produced, a dozen or more 

 in each stroma. Septate trichogynes project well above the leaf 

 surface. Spermatia adhere in great profusion to the trichogynes. 

 There seems little reason to doubt, both from Higgins' observa- 

 tions and from those of Backus (1934), that the spermatia func- 

 tion in fertilization. By spring, the apothecia have matured on 

 fallen leaves. 



Higgins (1914) also made the interesting observation that the 

 shot-hole effect is the result of cleavage of the glucoside amygda- 

 lin, by emulsin within invaded cells. In this cleavage of the 

 amygdahn molecule, two molecules of glucose, one of benzalde- 

 hyde, and one of prussic acid are formed. The increased osmotic 

 pressure resulting from the presence of glucose causes water to 

 be drawn from cells at the periphery of invaded ones, which swell 

 in consequence, and a line of abscission is developed. 



Nannfeldt also placed Diplocarpon in the tribe of Drepanape- 

 zizoideae. Among the species included in this genus are D. rosae, 

 causing black spot of roses, D. earliaiia, causing strawberry-leaf 

 scorch, and D. (Entojnopeziza) soraueri, causing pear-leaf spot. 

 Diplocarpon rosae is commonly known in its conidial stage as 

 Actinonevia rosae. Its morphology, however, is that of the form 

 Genus Alarssonia. The ascis^erous staore was first described 

 [Wolf (1912)] in 1912 and improperly assigned to the Micro- 

 thyriaceae. In late summer spermatia are produced in the conid- 

 ial acervuli [Wolf (1926)]. Coincidentally several ascogones are 

 developed in each apothecial initial. By spring the apothecia 

 have matured within decaying leaves. Occasional apothecia have 

 been noted to bear conidia, as has been recorded also [Backus 

 (1934)] for Higginsia hievialis. A similar course of develop- 



