THE CROWN GALL: TYPE 417 



Evans, of Pretoria, has reported still larger ones from the 

 willow in South Africa (20 inches long with a circumference of 

 4 feet, 7 inches). 



This disease is of a peculiar type: (1) in that the growth j 

 is extra-physiological and injurious to the rest of the plant, / 

 slowly dwarfing or killing it; (2) in that secondary tumors occur / 

 as growths from tumor-strands which are bedded deep in the / 

 normal tissues (Figs. 319, subs. 5, 6, and 323 to 325) and derived 

 by growth (cell-division), in the form of a continuous chain of \ 

 cells, from the primary tumor; and, finally, (3) in that the f 

 secondary tumors reproduce the structure of the tissues in which 

 the primary tumor has developed even when they appear in other 

 organs, thus if the primary growth is in the stem and the second- 

 ary is in a leaf, the attacked part of the leaf will be converted 

 into a pseudo-stem (Figs. 326 and 327, sub. 4). As bone is 

 often out of place in malignant animal tumors, so lignin may be 

 out of place in crown gall (Fig. 328). 



The largest tumors are developed out of the cambium, but 

 small ones may be produced by very shallow punctures into the 

 bark parenchyma and these become vascularized (Fig. 329). 

 I have not always been able to produce galls by inoculations 

 into the pith. Much depends on its age. The growth of the 

 tumor may stimulate multiplication of the surrounding uninocu- 

 lated tissues. For evidence of this, see the lower part of Figure 

 329 (under X) where large bark-parenchyma cells are subdivid- 

 ing, and (Fig. 319, subs. 5 and 6) where the wood is greatly 

 thickened on the side of the stem bearing the tumor strand. 



Attacked branches are frequently killed (Figs. 330 and 319, 

 sub. 3), but seldom is the whole plant killed, at least not for a 

 long time, if it is of any size when attacked. Attacked plants 

 are generally more or less stunted in their growth, especially if 



part of the shoot has developed the larger tumors, (la) On yellow Paris daisy, 

 showing tumor due to a single infected needle prick. Sterile pricks above. (2) 

 On peach. Time, 5 months, nearly. The organism used was plated from a 

 gall on the peach. 1908. (2a) On peach. Time, 18 days. (3) On apple. 

 Inoculation from peach, made high up on the stem by needle pricks. 1908- 

 % natural size. Time, 5 months. Stem above is dwarfed. (4) On European 

 grape. With bacteria plated from crown gall on poplar. Time, 44 days. 1910. 

 A serious disease on raisin grapes (Muscats) in California. 

 27 



