Parasitic and Saprophytic Fungi in Orchards. 193 



Some fresh leaves of Winesap and Ben Davis were placed in 

 sterile damp-chambers. Some of the hyphae were placed upon 

 the surface of the leaves. In a short time the characteristic 

 circular spots were formed similar to those attributed to Phyl- 

 losticta under natural conditions. These leaves were again 

 washed for a minute in mercuric chloride solution, rinsed o(T in 

 sterile water, and the spots removed and placed in glucose agar 

 plates. From the tissue of the spots filaments came which gave 

 the characteristic red color to the glucose agar and the further 

 growth proved that the cultures were Phyllosticta limitata. 



Leaves which were collected last fall were washed in mer- 

 curic chloride solution and then in water. ' Spots showing 

 pycnidia were cut out and transferred to glucose agar plates. 

 These, too, gave colonies, whose cultural characters were such 

 as have been found in the exposures. 



Since last autumn the fungus has not formed pycnidia in 

 any of the various media tried, consequently no spores have been 

 available for inoculations. 

 2. Nummularia discreta (Schv.-.) Tul. 



Nummularia discreta is the fungus which causes the canker 

 popularly known as the "Illinois apple-tree canker."* It is 

 one of the wound parasites, entering through the wounds left 

 by pruning or through those caused by the harness or apparatus 

 used in cultivation. The brown spherical spores genninate very 

 readily in water, so that the spores which lodge on the moist 

 surface of a wound are in very favorable condition for germina- 

 tion. The hyphae penetrate into the tissue of the tree, killing 

 the elements as they advance. 



In its early stages the bark has a dirty, brown appearance. 

 The spot which is cankered is usually depressed, small at first 

 and gradually increasing in size. Between the cankered and 

 living tissue there is always a distinct line of demarcation. The 

 depression is caused partly by the drying out of the tissue and 

 partially by the increased thickness of the sound bark. Late 

 in the summer or in the autumn the stromata are formed be- 

 neath the bark. In sectional outline these stromata are cup- 

 shaped. As the stroma grows older a ring of black stromatic 

 tissue is formed beneath the disc. This ring extends through 



•Hasselbring: Bulletin lU. Agd. Exp. Station. 70: 1902. 



