G 



Mycologia 



cross section to the left of the figure. The wood and pith are 

 apparently normal structurally though physiologically dead. 



A later state in the necrosis following the inoculation of Bac- 

 terium tumefaciens is shown in figure 6 photographed eleven 

 months afterward. Here again the inoculation was made at one 

 side of the stem in the third internode with a needle dipped into 

 an emulsion of the crown gall organism. In this late stage the 

 growth does not completely girdle the stem, yet two months previ- 

 ously the leaves f elr off and the stem became discolored and finally 

 died. The crown gall and the stem above the gall also died. A 

 short portion of the stem immediately below the gall at the time 

 of the photograph was rapidly undergoing similar changes. The 

 gall in this case again shows all the characteristics of the typical 

 crown galls referred to above. The outer surface is dry and 

 woody and is markedly nodular. In a longitudinal section of 

 this gall we find the region near the stem slightly moist, darker 

 in appearance and invading the wood cylinder (Fig. 7). A large 

 portion of the wood cylinder is intact and appears to be func- 

 tional. There again, it appears as if death was caused by Bac- 

 terium tumefaciens or the crown gall cells rather than by the 

 interference with the transportation system caused by the destruc- 

 tion on the invasion of the fibrovascular bundles. 



Figure 8 represents a gall 12 months old which has caused no 

 injury to the stem either above or below the gall. Growth is 

 continuing normally. The inoculation was made in two opposite 

 sides of the branch. The crown gall that appears in front on 

 the stem " B " and " C " was produced by inoculating an axillary 

 bud region. The lower gall, "A," was obtained by inoculating 

 an internodal space on the opposite sides of the stem. The lower 

 growth which appears as two separate tumors on opposite sides 

 of the stem consists of one continuous mass of tissue encircling 

 one half of the circumference of the stem. The growth has a 

 distinctly tubercular structure. It is dark brown in color, hard 

 and dry, and apparently dead. The upper crown gall which is 

 on the surface of the stem, as mentioned above, extends for a 

 distance of nearly one half of the circumference of the stem also. 

 To the left it developed into a more or less uniformly globular 

 growth through which two branches have grown. 



