THE FUNGI WHICH CAUSE PLANT DISEASE 275 



=Fuscicoccum veronense). Pycnidia formed on old leaves on 

 the ground, erumpent, subcuticular, brown, 200-300 /i; conidia 

 numerous, oblong, ovoid to fusoid, 7-11 x 3-i n. 



The conidial form on sycamore and oak, first described in 1848, 

 is common on leaves and young branches, the mycelium checking 

 the sap-flow and causing death of surround- 

 ing tissue. A stroma is formed on the outer 

 layers of the mesophyll and from this arise 

 the short conidiophores to constitute the 

 acervulus. 



Infection experiments by Tavel ^^ gave 

 negative results. Other infection experiments 

 have also been unsatisfactory. 



The ascigerous form was first found by 

 Klebahn'''^ on old leaves on which it ma- ^'^'a ™/'Iftr' Edl 

 tured about Christmas time. While the co- gerton. 

 nidia are uniform in shape four modes of development are found, 

 as stated above. 



Pure cultures from all the spore forms were compared by Edger- 

 ton ^^^ confirming Klebahn's conclusion as to their identity. Cul- 

 tures by Stoneman ^^' showed the forms on sycamore and oak to 

 be the same. 



G. leptostyla (Fr.) Ces. & d. Not. 



Perithecia conic, short-beaked; asci subclavate, 45-65 x 10-12 

 ju; spores fusoid, curved, 18-22 x 4 /i, hyaline. Conidial phase 

 (=Marssonia juglandis). Acervuli gregarious, hypophyllous, 

 rounded; conidia obovoid, 8-10 x 4^5 n, 1-septate, pointed 

 above, truncate below, greenish. 



The connection between the conidial and ascigerous forms was 

 demonstrated by Klebahn ^^ by pure cultures and by ascosporic 

 infection. The conidial form is common on walnut leaves; espe- 

 cially severe on the butter-nut (Juglans cinerea) often defoliating 

 this host in mid-summer. 



G. quercus-ilicis Berl. occurs on oak leaves in Italy. 



G. erythrostoma Auer. is the cause of a disease of cherry leaves 

 in Europe; 2'«' '^1 



G. padicola Kleb. is the ascigerous stage of Asteroma padi 

 which is widely distributed in Europe on Prunus. 



