220 TRANSACTIONS OF THE HORTICULTURAL 



If our government would begin this work at once, and every 

 agriculturalist and horticulturalist who is already alive to its import- 

 ance does his duty, ere another centennial America will again be 

 noted for her grand and magnificent forests. And with our present 

 resources we shall be in possession of all the elements necessary to 

 national wealth and prosperity, and all the conditions for rendering 

 our teeming millions an industrious and happy people. 



THE EFFECTS OF FROST ON THE TRUNKS OF APPLE TREES. 



BY T. J. BURRILL. OF CHAMPAIGN. 



Throughout the Northwest much damage has recently, espe- 

 cially daring the last three years, been done to the apple orchards by 

 injuries to the trees near the ground, but sometimes higher np the 

 trunk and branches. Rabbits, mice, and insects, each and all have 

 been the agents in a part of this destruction, yet sometimes they ap- 

 pear to be blamed more than their deserts, for though the work of 

 each can be easily identified, observers have not always been careful, 

 and have classed all kinds of injury together. We propose in this 

 paper to speak only of the effects of imf avorable climatic causes, save 

 a few words upon a still differently produced disease or injury, popu- 

 larly known as " sun scald." This last most often, but not always, 

 occurs on the south side of the tree, and is usually, but not always, 

 confined to well circumscribed areas. The bark dies, but adheres 

 firmly to the wood. Sometimes new bark forms beneath the old and 

 the repair is thus accomplished. The name sun scald is a misnomer. 

 The heat of the sun never really scalds any tree, and esj^ecially in 

 winter no such action should be attributed to the enfeebled rays. 

 The fact is, the chief part of this peculiar injury is accomplished 

 during the summer, and is due to blight bacteria, the same kind that 

 destroys the pear tree. The south side is more often affected because 

 the outer, corky layer of bark is there more deeply cracked, and the 

 living tissue exposed to the inroads of these fermenting agents. The 

 same thing has been artificially produced on the north side, and can 

 readily be started in any part of the bark of the trunk by inocula- 

 tion. I have elsewhere discussed this matter, and refer to the pub- 

 lished transactions of the Illinois and Indiana State Horticultural 

 Societies. There is abundant evidence of the correctness of this 

 statement of the cause of the trouble now described. Possibly the 

 bark in a given area may sometimes die and adhere from other causes, 

 ]>ut in very numerous observations by myself, not one such spot has 

 been seen which could not be confidently pronounced due to bacteria. 



The special injuries which are here attributed to frost are of two 

 kinds. In one the bark and the wood, or, the former alone, is split 

 so as to gape open until thawing occurs, when the crack may be 

 closed by the elasticity of the tissues, though healing does not take 

 place except perhaps by the overspreading of new groWth. This re- 



