324 Report OF THE BOTANICAL DEPARTMENT OF THE 
advance in the cambial zone are yet shrouded in mystery, 
though prolific theoretical explanations have been given. Is 
it possible that the occurrence of a “ fire blight” epidemic is 
fundamentally dependent upon how the trees came through 
the previous winter rather than upon the weather of spring 
and early summer? Is “ fire blight” only the sudden drying 
of such twigs as were winter-injured to a certain degree, at 
their ““ branch rings” of normally excessive cortical and me- 
dullary tissues? 
WINTER-HARDINESS OF TREES. 
There is not much definite to be said regarding hardy and 
susceptible varieties as related to Crown-rot or other frost- 
injuries, because all observations have been too limited and 
fragmentary. If trees are to be grown in regions of deep, 
all-winter snows, the winter-hardiness of roots is not as im- 
portant as that of the trunks and branches; however, in re- 
gions of uncertain snows the hardiness of roots must be con- 
sidered first. 
As regards varieties and stocks.— Nearly all of our most 
desirable varieties of winter apples have been reported, by 
some one or other, as liable to winter-injury and the numerous 
ills which follow in its wake. Though, of course, some are 
more winter-hardy than others. Macoun’s** report on “ The 
relation of winter apples to hardiness of trees” shows that 
79 per ct. of all winter-killed trees are winter varieties. He 
suggests that the ancestors of seedlings be short-seasoned va- 
rieties. Early-maturing varieties were also found more resis- 
tant by C. Baltet.® Emerson’s suggestion that the early ma- 
turity habit is often more important than constitutional hardi- 
ness to frost, may prove of value. It seems to be still an open 
question to what extent, if at all, a stock of an habitually early 
variety may influence the ripening habit of a scion from a late- 

*% Canad. Hort., 29: 291-2. 1906. 
De Vaction du froid sur les végétaux pendant Vhiver 1879-80. Mem. 
Soc. Nat. Agr. France, 127: 1-340. 1882. 
