THE FUNGI WHICH CAUSE PLANT DISEASE 409 



leaves. The cambium layer is the seat of the disease. The fungus 

 spreads rapidly but is not a serious pathogen except in rainy periods 

 in midsummer. 



C. javanicum (Hen.) S. & S. causes disease of coffee and tea; ^ 

 C. dendriticum Hen. parasitizes orange stems; ^* C. comedens 

 (Nees) Fr. occurs on oak as a wound parasite; C. zimmennannii 

 S. & Syd. injures many tropical trees; ^ C. lilacino-fuscum Berk. 

 & Curt, occurs on cacao. 



C. chiysanthemi Plow, is reported as the cause of death of 

 cultivated chrysanthemiun in England. 



Protocoronospora Atkinson & Edgerton (p. 405) 



Genus as in Corticium, except for the basidia which bear 4-8 

 sessile, oblong or elliptic spores. 



P. nigricans Atk. & Edg.*' forms narrow elongate spots on vetch 

 pods, stems and leaves. Spot, oblique on the pods, 2-5 x 1-2 mm., 

 at first white or with a purple border, later black; subhymenial 

 layer subepidermal two or three cell layers thick; basidia clavate, 

 to subcylindric, 20-30 x 6-8 n; spores sessile, pale-pink in mass, 

 oblong to subelliptic, hyaline, smooth, granular, continuous, or 

 1-septate in germination, straight or curved. Found on vetch at 

 Ithaca, N. Y., associated with Ascochyta. 



Stereum Persoon (p. 405) 



Hymenophore leathery or woody, persistent, of several layers, 

 sometimes perennial, laterally or centrally attached; hymenium 

 smooth. 



A genus of about two hundred fifty species chiefly wood in- 

 habiting, but a few grow in humus. 



S. hirsutum (Willd.) Pers. 



Hymenophore leathery, firm, expanded, wrinkled, hairy, yellow- 

 ish; the hymenium yellowish, smooth. 



It causes a rot of oak in which the wood appears white-spotted 

 in cross section. 



S. quercinum Potter,*^ is found on oak in Europe. 



S. frustulosum (Pers.) Fries, though sometimes found on living 

 trees, is confined to dead wood. It causes a speckled rot of oak 

 wood.«^ Fig. 295. 



