THE FUNGI WHICH CAUSE PLANT DISEASE 511 



More than twenty-five species, chiefly saprophytes. 

 M. anthiirii Trinch. occurs on Antliurium. 



Diplodia Fries (p. 510) 



Pyenidia immersed, erumpent, carbonous, black, usually 

 ostiolate-papillate; conidia ellipsoid or ovate; conidiophores 

 needle-shaped, simple, hyaline. 



Over four hundred fifty species, many of them saproph3i;es. 



D. zeae (Schw.) Lev}"^-^"'' 



On ears and stalks of com, pyenidia borne on the husks, cobs, 

 stalks and rarely the grains, gregarious, small, lenticular to flask- 

 shaped or irregular, papillate; conidia elliptic, straight or curved, 

 constricted or not, 25-30 x6 n. 



It occurs as the cause of a very serious dry rot of ear corn. 



The actual growing mycelium is hyaline and much branched. 



Pyenidia in the cob are principally on the scales which surround 

 the inner ends of the kernels and are set in a dense mass of white 

 mycelium. On dead stalks 

 the pyenidia form below 

 the rind, particularly at 

 the nodes, breaking 

 through during the follow- 

 ing summer, and extruding 

 the spores in cirri. 



The fungus was studied 

 extensively Ijy Burrill & 

 Barrett ^"^ and inoculations -"""vma 



were made using pure cul- ^"^^ 353^;j;Py-'f 1°^,'^^]°^^^- -" ''"" 

 tures. Spores placed under 



the husk or in the silk, or sprayed upon plants in suspensions, re- 

 sulted in disease. 



Smith and Hedges "* report that infection is often by way of the 

 root system, the mycelium reaching the grains through the stem 

 and from the cob. 



D. macrospora Ea. 



Pyenidia scattered, large, erumpent, carbonous; conidia elon- 

 gate, irregularly clavate, curved or constricted, 70-80 x 6-8 fi. 



