318 REpoRT OF THE BOTANICAL DEPARTMENT OF THE 
Morse’s explanations of the cause of crotch-injury violate 
certain physical laws. 
To obtain definite information upon the question of frost- 
injury, young fruit and forest trees were subjected to induced 
low temperatures in a large double-walled cylinder, by Sorauer. 
On a potted sweet-cherry tree exposed in May to —7° C. over 
night, all except the youngest leaves were killed and browned. 
An odor of roasted cherry wood was noticeable during the 
first week after removal from the freezing apparatus. 
The fibro-vascular bundles, of the venation in older leaves, 
were often brown, while the intercostal regions were normally 
green. Hard-bast elements were the first to become browned, 
followed by the browning of the epidermis-cell contents. The 
smaller spiral vessels were browned before the larger ones. 
The most susceptible region on a trunk or limb was found 
to be at the points of origin of twigs or branches. A section 
through a branch at the origin-point of a spur or side-branch 
shows that the whole of the normally excessive cortical paren- 
chyma was browned and cleft at a number of places. The 
cambial zone had its cambium mostly uninjured, but both the 
young wood and bast cells on either side were browned. The 
wood cylinder, where it branches off from an axis, has its 
wood-cell bundles much separated by medullary rays which in 
the frozen tree had become browned, thus leaving only narrow 
ribbons of living wood sandwiched in between browned rays 
and the dead pith and cortex. The pith and wood cylinder 
of the avis were uninjured, though its rays near the spur had 
become browned. The small groups of primitive xylem cells 
in the outer parts of the pith were also browned. ‘The effect 
on the one-year-old parts of branches was decidedly different. 
The injury was generally more pronounced on one side than 
on the other, forming frost-blisters on the bark. The pith was 
split, leaving a hollow center surrounded by collapsed, browned 
cells, though the other pith cells seemed mostly uninjured. 
Separation always occurred at the middle-lamelle. 
A section through the transition region from the one-year- 
old to the spring growth revealed some interesting facts. The 
