286 MANUAL OF POISONOUS PLANTS 



Janczewski who has studied the life history of Septoria graminum states 

 that this represents the pycnidial stage of Leptosphaeria tritici and that the 

 conidial form is the Cladosporium herbarum. We have not found the Septoria 

 in Iowa though the Cladosporium is common. 



The Septoria tritici Desm. is closely related to the above and should per- 

 haps be regarded as nothing more than a variable form oi S. graminum. 

 The spots it produces are at first yellow, then reddish-brown, and finally 

 whitish. The spores are 50-60 M long and 1-5 to 2 A» wide and usually divided. 

 A Septoria on the glumes of wheat in Ohio has been reported by Selby. 



Several other species of Septoria are allied to the above species, one, the 

 Septoria bromi Sacc. is common in Iowa on Bromus secalinus. 



Diplodia, Fr. 



Perithecia bursting out sub-cutaneously, sub-carbonaceous, papillate ac- 

 cording to type; spores ellipsoidal, ovoid or oblong, 1-celled, fuscous, per- 

 forated; basidia rod-like, simple hyaline. From the original genus have been 

 separated five genera as follows: Species with superficial perithecia Diplodi- 

 ella; with hirsute perithecia Chaetodiplodia; with clustered perithecia Botry- 

 odiplodia; with mucilaginous spores Macrodiplodia; with hyahne spores 

 Diplodina. 



Fig. 103. Spores of Diplodia Zeae. 2. Young spores on the conidiophores with sporo- 

 phores attached. 3. Germinating spores. 4. Dark swollen hyphae of Diplodia. 



Diplodia Zeae (Schw.) Lev. 



Pycnidia black and spherical to pyriform, those forming on the husk or 

 stalk developing within the tissues and breaking through at maturity, the 

 greater number of pycnidia, however, occur between the kernels and are sit- 

 uated in a stroma. Conidia dark brown, cylindrical to elliptical, obtuse, straight 

 or usually slightly curved and 1-septate; one to several oil drops in each cell; 

 5m in diameter; spores germinate in 18-24 hours in 3 per cent glucose agar 

 at 26° C ; in somewhat longer time when grown on corn agar ; germ tube arises 

 from near distal end at each spore.* 



Distribution. A serious parasitic disease generally found where corn 

 is cultivated, particularly in Illinois,* Iowa, and Nebraska. 



Poisonous properties. This fungus is widely distributed in ears of corn and 

 may be responsible for forage poisoning. 



♦ Heald, F. D. ; Wilcox, E. M. ; and Pool, V. W. The Life-history and Parasitism of 

 Diplodia Zeae (Schw.) Lev. 



• Burrill, T. J., and Barrett, J. T. Ear Rots of Corn. Bull. 111. Agr. Exp. Sta. 

 133:65-109. ii pi. 



