WINTER INJURY IN RELATION TO SPECIFIC FRUITS 321 



July 15 and Dec. 26, from 60.4 to 45.7 per cent., having on that date the 

 lowest water content. It is also the least hardy of the varieties under 

 consideration. The hardier varieties were found to lose less water 

 through the bark in a given time. 



Various workers have studied the structure of apple twigs but no one 

 has been able to correlate definitely any structural differences with hardi- 

 ness or its lack. There seems some tendency for hardier varieties to 

 have somewhat thicker bark and more starch in their tissues but these 

 characters are by no means constant. Were the starch content shown to 

 be correlated, it could hardly be regarded as a causal agent but more 

 likely a product of the conditions that make the variety hardy, through 

 making it mature. 



In short, then, the only character that can be linked definitely with 

 hardiness in the apple is maturity. If one variety is hardier than another 

 because it matures better, the cultural practices that make the tender 

 variety mature better make it in effect more hardy. A well matured 

 tree of a tender variety is undoubtedly more hardy than an immature 

 tree of a hardy variety. This accounts for many apparent inconsistencies 

 in field observations. 



Control Measures. — Efforts have been made to influence cold resist- 

 ance by topworking upon stocks of great hardiness. In so far as root 

 killing is prevented this practice has proved beneficial. It is also a wise 

 practice if the growing of varieties notoriously subject to crown rot or 

 crotch injury is to be undertaken. However, that hardiness of stock 

 increases the hardiness of the cion is not shown conclusively by any 

 evidence available. It is conceivable that an early maturing stock might 

 influence the top slightly in the same direction but any influence of this 

 character is comparatively insignificant. Macoun^^^ reports top grafting 

 varieties not perfectly hardy on stocks of very hardy varieties at Ottawa, 

 Ontario; among the cions used were Baldwin, Benoni, Esopus, Fallawater, 

 King, Newtown, Northern Spy, Ontario, Rhode Island, Rome Beauty, 

 Sutton, Wagener, Winesap and York Imperial; the stocks used were 

 McMahon, Gideon, Haas and Hibernal. The grafts endured several 

 winters, but "the test winter of 1903-1904 killed practically all of them," 

 though the stocks survived. It is, however, interesting to note that 

 Sorauer^^^ considered that grafting of weak growing varieties upon 

 vigorous stocks results in an increased amount of frost canker, character- 

 istic of immature tissues. 



There is a limit to the effects that can be induced by cultivation. 

 No amount of cultural manipulations can make a variety mature its 

 fruit and its wood in a situation where it does not receive sufficient heat 

 (where the season is too short). It is not without significance that only 

 one of the important winter apples of the south can be grown to any 

 advantage in the north. Whether the cause be called failure to mature 



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