ORDER MONILIALES (hYPHOMYCETEAE) 597 





-X f"^^~SZ: Fig. 202. Moniliales, 



Family Dematiaceae. (A) 



Stemphylium sarcinaeforme 



(Cav.) Wilts. (B) Alternaria 



e tenuis Auct. (sensu Wilt- 



^ ^ shire 1933). (A, courtesy, 



Groves and Skolko: Can. J. 

 Research, 22(4):190-199. B, 

 ibid., 22(5) -.217-234.) 



■\ '} 



B 



and in some species has a constriction at the median transverse septum. 

 The conidiophore may be shghtly swollen at its apex. The perfect stage of 

 S. botryosum Wallr. is Pleospora herharuni (Pers.) Rabenh., a fungus 

 belonging to the Sphaeriales or Pseudosphaeriales and widespread the 

 world over. It occurs, apparently, in many strains on all sorts of hosts, 

 probably developing mostly only in the saprophytic stage of growth. The 

 perfect stages of the other species of Stemphylium are not known. S. 

 sarcinaeforme (Cav.) Wilts, is a frequent cause of sometimes serious leaf 

 injury of various species of Trifolium. Its spores are smooth whereas those 

 of S. botryosum are roughened. The genus Sporodesmium, with often 

 roughened conidia occurring singly on rather short conidiophores is of 

 interest because it sometimes is the imperfect stage of species of Hy- 

 steriales. (Fig. 202.) 



Two genera of great economic importance with long, slender spores 

 (Scolecosporae) are Cercospora and Cercosporella. These differ only in the 

 presence of a brown pigment in the conidiophores and sometimes the 

 spores of the former and its absence in the latter. Since, however, this 

 pigmentation varies in degree with the age of the fungus and external 

 conditions there is no real basis for their separation except convenience. 

 Cercospora is placed in the form family Dematiaceae and Cercosporella in 

 the Moniliaceae. The conidiophores emerge through the stomatal open- 

 ings in tufts of varying number, from a pseudoparenchymatous mass of 

 cells that lies beneath the stoma or sometimes projects through it a little. 



