ORDER PSEUDOSPHAERIALES 



297 



Native to North America it has been introduced into Europe where it 

 has caused great damage to the more susceptible Vilis vinifera L. The 

 fungus attacks the leaves on which it produces brown dead spots and the 

 fruits which become dark-colored and shrunken. In these leaf spots and 



Fig. 96. Pseudosphaeriales, Family Pseudo- 

 sphaeriaceae. Pyrenophora teres (Died.) Drechsl. (A) 

 Conidiophores and conidia {Helminthosporium teres 

 Sacc). (B) Perithecium. (C) Asci in cavities dissolved 

 in the stromatic tissue. (Courtesy, Drechsler: /. Agr. 

 Research, 24(8):641-740.) 



shriveled berries are produced numerous pycnidia in which arise hyaline, 

 ellipsoidal spores {Phoma stage of the fungus). In the leaves and berries 

 which overwinter on the ground there develop perithecium-like structures 

 in which are produced clusters of eight-spored asci. Paraphyses are not 

 present. Each hyaline ascospore just at maturity forms a septum dividing 

 it into two quite unequal parts. The formation in pycnidium-like struc- 

 tures of "microconidia" which do not appear to be capable of germination 



