92 BACTERIA IN RELATION TO PLANT DISEASES. 
ATROPHIES. 
The olive-tubercle, due to Bact. savastanoi, affords an excellent example of atrophy. 
When the tubercle occurs on young stems that portion of the stem beyond the abnormal 
growth is robbed of a large portion of its nourishment and often dies outright. In less 
severe cases it is very common to find the length of a stem greatly reduced as compared 
with normal shoots of the same age and origin. The diameter of the stem immediately 
above the tubercle is also perceptibly less. Often it is not one-half or one-third as big as 
the stem iinmediately below the excrescence (see plate 9). Often also the leaves are dwarfed 
on that part of the shoot beyond the tubercle. Not infrequently when the terminal shoot 
becomes diseased in this way an inconspicuous side shoot takes the lead and becomes the 
strong shoot. 
Fig. 28.* 
The same thing occurs in the daisy knot, due to Bact. tumefaciens. As growth of the 
knot continues, branches are often starved out and die (plate 10). 
There is also a dwarfing of the whole plant in certain cases. This occurs very often 
in sweet corn attacked by Bact. stewarti, in cane attacked by Bact. vascularum, in seedling 
cabbages attacked by Bact. campestre, and in many plants attacked by crown-galls and 
root-galls. 
ENLARGEMENT OF THE NUCLEUS. 
In many diseases which I have studied I have not been able to make out any change 
in the form or size of the nucleus, those nuclei near diseased areas being not different from 
more remote ones. The change in such cases, if any, is a simple disintegration under the 
action of the bacteria. In olive-tubercle, however, and in the crown-gall there seems to be 
*Fic. 28.—Tumors on sugar-beets due to inoculation by needle-pricks with Bact. tumefaciens, plated from Paris 
daisy. Inoculated about six weeks. Photographed April 1907. Nearly natural size. 
