New YorK AGRICULTURAL EXPERIMENT STATION. 319 
wood cylinder is small and was found to be split at the thick 
medullary rays. The fibro-vascular bundles were completely 
surrounded by browned parenchyma and isolated from the 
uninjured cambium and but slightly browned bark. The pith 
was not affected. This state of things could be followed down 
into the year-old twig, where, however, the wood cylinder was 
not separated from the bark. 
Radial clefts in the wood and cortex are said to be caused 
by the tangential contraction of the twig’s tissues. Since the 
wood and cortex-parenchyma cells can distend but little, rup- 
tures occur at the middle-lamellze of the medullary rays. The 
Separated wood-ray cells were browned, but the bark-ray cells 
seemed uninjured and soon closed their clefts. The cambium 
cells, however, distend readily and were therefore generally 
found intact and unaffected. These observations are thought 
to show that differing tissue-tensions and not ice-formation 
are the causes of clefts and cracks. 
Sour-cherry trees given the same treatment were not affected 
in exactly the same way. Fewer and smaller clefts were 
formed, a stoppage of the vessels with gum seemed to occur. 
It is thought the excessive formation of gorged, imperfect 
cells in the greatly reduced growing regions of a much-injured 
tree may lead to a disorganizing gummosis of the abnormal 
tissues. 
The cleft formation occurs also in pear and apple branches 
when subjected to the freezing treatment. The same differ- 
ences were observed between the effect in the terminal and 
basal ends of branches as described for sweet cherry. To de- 
termine how far low-temperature injuries can extend down the 
wood of an externally unaffected twig, an apple-tree shoot, hay- 
ing a new spring growth of 4—6 cm., was subjected to —6° C. 
overnight. The spring wood was entirely killed and the wood 
cylinder of the one-year-old part as browned down 15 cm. The 
dormant buds were not killed but their spiral vessels were 
browned. Some of the branches of a five-year-old pear seed- 
ling were subjected to a temperature of —7° C. over night. 
Most of the leaves turned black, many having frost-blisters, 
