338 



The Mycelium. — The germ-tube as it branches lo develop the mycelium 

 is at first hyaline, but soon becomes darker. In old cultui'es it is very dark 

 brown. The conlciits ;uv tiranular, glycogen frequently being in-escut. Its 

 diameter ranges Iroin 4-li) microns; averaging about 7 microns. 



The ascogonous form lias been reported by Shear ('10)/ who sowed 

 ascopores of Melanops quercuum (Sehw.) Rehm forma tit is Sacc. and 

 obtained brown pycnospores which agree morphologically with those of 

 »S. malorum Pk. and Diplodia pseudo-Diplodia Fckl. 



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

 media which 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 hyphjie until only the extreme surface threads remain a light 

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

 expei-ience, and at present we liave about fifty different strains growing. 

 Wlietlier or not certain strains will not fruit in culture remains to be 

 tested. 



CONTROL 



Preventive measures have not been carefully worked out, though a 

 few general suggestions can be given. 



So far as an immediate remedy is concerned it seems that eradica- 

 tiun, protection and inuaunizntion are points most worthy of (•<insidera- 

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

 Cankers should be clean(>d out and this done carefully. Whether this is 

 practicable or not depi'uds upon the energies of the grower. In one or- 

 chard of about 400 trees which we call to mind, the work was done ef- 

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

 kered sj)ots, all diseased bark should be removed, the wiuiiids disinfected 

 with c(»rrosive sublimate (1-1000) and painted witii coal gas tar. Tools 

 which W(> have found convenient are those which any farmer has. namely, 

 a draw-shave, a farrier's kiufe for trinnuiiig the margin of the wound, 

 and the necessarv coal tar and disinfeclant. In jierfornnng these opera- 

 tions, as well :is when picking the fiMiit. it is i-econunended tlie work- 

 men usi' cai-e ;di(iui lirciiking (he hark. .\ny such wounds are only an 

 oi>en door for (lie fungus. 



''10. Shear, C. L. Life History i>f ^filanoim tiucrruuni iS-lnv.'i Rohm, /orwa vilis S^cc. 

 Scionco n. 8. 31:748. igid. 



