4 



Mycologia 



dipped into a culture of Bacterium tumefaciens. As few as 

 five pricks of the needles with the crown gall organism were found 

 to be sufficient to produce a visible neoplasm in a month's time. 

 A careful scrutiny of this picture reveals a number of galls at the 

 internodes of several branches (Fig. i, a, b) on the mid-vein of 

 an old leaf (Fig. i, c) and on one of the main branches (Fig. 

 I, d). Where the needle perforated the tissue a crown gall 

 was formed on both sides of the stem or the leaf. No less active 

 were the growths that were produced on the trunk of the tree 

 (Fig. i, d). The galls formed are of the characteristic type de- 

 scribed by Tourney, Smith and others. They are always firm, 

 yellowish in color and covered with brownish patches when 

 young and become dark brown in color and of a woody con- 

 sistency with age, as we shall see below. 



The crown gall, at this stage, as far as can be seen, has no 

 specially injurious effect upon the host. The terminal buds of 

 the plant are actively growing and there appears to be no signs of 

 dwarfing of the branches, nor any indication of fascination of the 

 internodes above the region of inoculation such as those reported 

 by Smith, and Levin and Levine for Geranium, Ricinus, etc. 



Figure 2 represents a branch from another rubber tree which 

 had been inoculated seven months previously on the second inter- 

 node. The crown gall has grown extensively, covering one half 

 of the circumference of the stem. The surface is dark brown in 

 color, highly convoluted, indicating a number of centers of pe- 

 ripheral growth. The mass is hard and some parts of the surface 

 appear to be dead. The branch however has grown considerably 

 as shown by the number of internodes above the crown gall. 

 (See Figs. 2 and 3.) In June, 1919, it was noted that the 

 terminal bud was small and dark green in color, and showed no 

 signs of growth. This was true of a number of other branches 

 which had been inoculated for the same length of time. The 

 control branches that were similarly treated with a sterile needle 

 had long greenish buds, many of which were opening. This condi- 

 tion suggested at once the possibility of mechanical interference 

 of the crown gall with the water supply of the plant due to partial 

 destruction and possible occlusion of the fibrovascular bundles, 



