THE FUNGI WHICH CAUSE PLANT DISEASE 509 



confluent, marginally fimbriate, the radiating fibers arachnoid, 

 white, distinctly branched; pycnidia tuberculariform, scattered 

 or confluent, black; conidia oblong, constricted, 18-20 x 5. /i; 

 conidiophores short. 



This fungus was first described in 1826. It is common on rose 

 leaves. The mycelium is in part subcuticular, in part deeper. 

 The subcuticular part is visible through the cuticle, consisting 

 of radiate strands each composed of several parallel hyphae. From 

 this mycelium branches penetrate deep into the leaf. The dark 

 color of the leaf spots is due to discoloration of the contents of the 

 diseased cells; the mycelium itself having little or no color. 



A. tiliae All. causes defoliation of Tilia. 



A. fagicola All. occurs on beech leaves; 



A. frazani All. on ash. 



Diplodina Westendorp (p. 505) 



Pycnidia immersed or erumpent, globose; ostiole papillate, 

 black, small; spores elongate. 

 It differs from Diplodia only 

 in the hyaline spores. 



About eighty species chiefly 

 saprophytes. 



D. citrullina (C. O. Sm.) 

 Gres. on cucurbs=Mycosph2e- 

 rella ciruUina. See p. 246. 



D. castanese P. & D. in- Fig. 352.-D. castaneEe, pycnidium and 

 u. baotcux^^c^ i . u, a-^. i spores. After Delaeroiz. 



jures chestnut leaves, and 



causes cankers on the shoots in France, resulting in serious 



loss.io^ 



D. parasitica (Hart.) Prill, occurs on the basal leaves of young 

 shoots of spruce causing defoliation. 



D. salicina C. & M. causes tips of willows to die. 



D. corticola A. & S. is found on cacao in Africa. 



Sphaerioidacea-PhaBodidymae (p. 480) 

 Conidia dark, 1-septate, ovoid to oblong. 



