278 



THE FUNGI WHICH CAUSE PLANT DISEASE 



Spores muriform 

 Stroma e£Fused 



Spores hyaline 8. Thyridella. 



Spores colored 9. Thyridium. 



Stroma none or pulvinate 10. Fenestella. 



Valsa Fries (p. 277) 



Perithecia on a more or less definite stroma, immersed, the 

 ostiole erumpent, black, firm; asci globose to cylindric, often 



long-pedunculate; spores 

 1-celled, rarely 2-celled, 

 cylindric, rounded, hya- 

 line or light-brown; pa- 

 raphyses none. 

 V. leucostoma (Pers.) 



Fr, 



12, 229, 280 



Fig. 207 



-Valsa. A, habit sketch; B, perithecia; 

 C asci. After Tulasue. 



Stroma strongly con- 

 vex, 2-3 mm., whitish 

 and granular within, outer layer coriaceous; perithecia immersed; 

 asci fusoid-clavate, subsessile, 35-45 x 7-8 m; spores biseriate, 

 allantoid, hyaline, slightly curved, 9-12 x 2-2.5 /i. 



Conidia (=Cytospora rubescens); stromate, erumpent, reddish; 

 conidia allantoid, 4 /*. On pome and stone fruits throughout 

 Europe, Australia and America causing the disease known as 

 " dieback." The fimgus was studied by Rolfs '"'• ''* who worked 

 out its life cycle. 



V. oxystoma Rehm. occurs on Alnus in Em*ope; 



V. (Eutypa) caulivora Rehm. affects Hevea. 



V. ambiens Fr. is on the apple in Europe. 



V. (Eutypella) prunastri (Pers.) Fr. is the cause of serious dis- 

 eases of apples, plums, etc., in England. 



V. (Eutypa) erumpens Mas. is reported as a wound parasite 

 in the tropics on Ficus, and cacao. 



Diaporfhe Nitschke (p. 277) 



Stroma very variable, usually definite; perithecia membranous 

 subcoriaceous, generally pale-cinereous within, with a cylindric 

 or filiform beak; asci fusoid; spores fusoid to subelliptic, 2-celled, 



