12 BULLETIN 191 



ten days to two weeks being required before visible growth could be 

 detected in the tubes. Plate IV shows a photograph of a six-weeks- 

 old culture on lima bean agar. During the first stages of the growth 

 the hyphae, (that is to say, the filaments of the fungus), were pure 

 white in color. They spread over the entire upper surface of the media, 

 forming a mat about one-sixteenth of an inch in thickness. In no case 

 did they penetrate the media to any extent. 



Inoculations were made upon media in deep petri-dishes, about 

 2.5 inches deep and 3.5 inches in diameter, in order to promote a longer 

 period of mycelial growth before the media began to dry. The growth 

 in the petri-dishes was not essentially different from that in the tubes. 



In all cases the mycelium retained its white color for a period of 

 from six to eight weeks, then slowly turned to a brown which grew 

 steadily darker for about eight weeks, after which time there seemed 

 to be little increase in amount of mycelium and no change in color. 

 The brown color exhibited so uniformly by the culture apparently 

 is due to a sort of incrustation which is laid down about the mass of 

 mycelium. The fact that this incrustation is soluble in part in potassium 

 hydroxid and entirely in warm nitric acid indicates, as Von Schrenk (2) 

 has stated, that it is due to the presence of decomposition products. This 

 coloring matter diffused through and stained brown the lima bean agar 

 after two months. The growths on the two kinds of media differed 

 only in minor particulars. 



Sterile wood cultures. In order more closely to follow the fungus 

 in its attack upon wood, cultures were made in the following manner : 

 Small blocks were sawed from each of seven different kinds of healthy 

 wood, spruce, pine, hemlock, tamarack, balsam, birch and oak. These 

 blocks were taken from the trunks or branches and sawed in such a 

 manner that both heart-wood and sap-wood were present in each block. 

 They then were put into an ordinary test tube, in the bottom of which 

 had been placed previously a small ball of water-soaked cotton. The 

 tubes then were plugged and sterilized. Inoculation was accomplished 

 by introducing small particles of mycelium from previous media cul- 

 tures. Growth in the dark and at room temperature started on the 

 wood almost immediately and spread irregularly over the entire sur- 

 face of the block. Eight inoculations, besides a check, were made on 

 each kind of wood and in 95 percent of the tubes the cultures ap- 

 peared pure. The fungus apparently showed no preference for the 

 sap-wood. 



Growth on different species. Comparison of the amount of hyphae 



