352 The Principles of Fruit-growing. 
the open in regions where the ground freezes 
deep. This subject of the root-galls has been 
fully gone over by various writers, and a summary 
of the subject is presented in Bulletin 117 of the 
Cornell Experiment Station (although this subject is 
by no means well understood), from which the fol- 
lowing epitome is clipped: “The conclusion of the 
whole matter, then, as we now 
understand it, is that these root- 
galls are not the work of a par- 
asite, but are a mal-forma- 
tion following some injury of 
the root, or some uncongenial 
condition in soil or treatment. 
The galls may seriously interfere 
with the nutrition of the plant, 
in many cases causing it to be- 
come weak and sickly. It is 
probable that the trouble is not 
communicable, and that cutting 
; off the gall averts further trouble 
Fig. 65. Injuries by hail- 
stiaes, from that source. As a precau- 
tionary measure, however, we 
much prefer to plant only trees with perfectly clean 
and normal roots.” 
The injuries caused by hail are very often con- 
founded with those wrought by borers and other 
pests, and it is the delight of many persons to en- 
deavor to puzzle the experimenters and teachers with 
specimens of such work. Plum limbs injured by 
hail-stones are shown natural size in Fig. 65, 
