338 



The Mycelium. — The germ-tube as it branches to develop the luycelium 

 is at first hyaline, but soon becomes darker. In old cultures it is very dark 

 brown. The contents are granular, glycogen frequently being present. Its 

 diameter ranges from 4-10 microns ; averaging about 7 microns. 



The ascogonous form has been reported by Shear ('10),^ who sowed 

 ascopores of Mclanops qnerctium (Schw. ) Rehm forma vitis Sacc. and 

 obtained brown pycnospores which agree morphologically with those of 

 »?. malorum Pk. and Diplodia pseudo-Diplodm Fckl. 



Pure Cultures. — The fungus grows and fruits well on any of the 

 media whidi we have used, including several vegetable and fruit decoc- 

 tion agars. Growth is at first cottony, the colonies effuse and radiating. 

 The brown color characteristic of the older threads soon spreads through 

 the aerial hyph;e until only the extreme surface threads remain a light 

 gray color. The production of pycnidia in culture has never failed in our 

 experience, and at present we have about fifty different strains growing. 

 Whether or not <-eitMin strains will not fruit in culture remains to be 

 tested. 



CONTROL 



Preventive measures have not been (arcfully worked nut, though a 

 few general suggestions can be given. 



So far as an immediate reme^ly is concerned it seems that eradica- 

 tion, protection and imnnini/ation arc jtoiiits most wortliy of considera- 

 tion. Clean culture should be jiracticed along with surgical measures. 

 Cankers should l)e cleancKl out and this done carefully. Wiiether this is 

 practicable or not dciicnds iii>oii the energies of the grower. In one or- 

 chard of about 4()0 trees whidi we call to mind, the work was done ef- 

 fectively at a cost of about twenty-five cents per tree. In removing can- 

 kered sjKits, all diseased bark should be removed, the wounds disinfected 

 with corrosive sublimate (1-10()0) and painted with coal gas tar. Tools 

 which we have found convenient are those which any farmer has, namely, 

 a draw-shave, a farrier's knife foi' triniiiiing tlie margin of the wound, 

 and the necessary coal tar and disinfectant. In ])erformiiig these opera- 

 ticHis. as well as when picking the fruit, it is reconunen<le(l the work- 

 men use cure about breaking the Itark. Any such wounds are oidy an 

 o]>eu door for the finigus. 



''10. Shear, C. L. Life History of Melanops querruum (S"h.v.) Retim. forma vitis Sacc. 

 Science n.s. 31:748. 1910. 



