1922] Essig: Morphology of Schizophyllum commune Fries 469 



hyphae had not penetrated through the fresh, uninjured bark, or cor- 

 tical tissues, or through the wood tissues in a lateral direction, but had 

 grown through the wood in the direction of the tracheae. 



Attempts to prove the parasitism of this organism were made by 

 Grueguen (1901) and Fulton (1912) with negative results. Rumbold 

 (1910) stated that Tuzson (1905), (whose paper is not available) grew 

 the fungus upon fresh (frais) beech wood. Kellogg (1915) was not 

 able to demonstrate the mycelium of Schizophyllum in the inoculations 

 made upon fruit trees. 



In my inoculation experiments young fruit trees of apple, pear, 

 and plum were used. Inoculations were made from agar plates of 

 pure cultures of the mycelium. The limbs of these trees were either 

 split through the center or cut into from the surface to varying depths. 

 A sterile knife was used in the incisions. The mycelium with sub- 

 stratum was transferred to the cut or slit surface and the wound was 

 tied up with string and covered wi'th waxed paper, a layer of wet 

 absorbent cotton, and another layer of waxed paper. The purpose of 

 the wet cotton and waxed paper was to prevent the drying out of the 

 exposed surfaces. At intervals of one week after the time of inocu- 

 lation certain limbs were removed, examined, and sections made to 

 determine if there had been any growth of the mycelium into the 

 living tissues. In most cases no trace of the mycelium could be found 

 in the wood. In two or three branches there was a darkening of the 

 surface exposed to the mycelium, and in the vessels the typical exudate 

 which is produced by the mycelium, but so little mycelium was found 

 in the ducts that the growth could' not be identified, with certainty, 

 as Schizophyllum. In only one branch was there an unmistakable 

 infection. This was in a limb of a plum tree cut off three months 

 after inoculation. The mycelium had penetrated to a maximum depth 

 of 3 mm. and the infected area was about 4 cm. long and 1 cm. in 

 width. Many hyphae were present in the vessels, and a few could be 

 seen in the medullary ray cells. There was the characteristic darkened 

 layer at the edge of the infection about 0.5 mm. thick. From the 

 results of previous investigations and these experiments it is evident 

 that the living woody tissues can be penetrated and killed by the 

 mycelium of Schizophyllum, but that this process takes place slowly 

 and with difficulty. 



