PLANT dise;ases IX 1908. 13 



soil, whether moist or dry, frozen or thawed, the amount of 

 water in the tissues at the time low temperatures occur, the 

 abruptness of temperature changes, the rapidity of thawing, the 

 direction and character of }.reaviHng winds, e. g. as influencing 

 the rate of evaporation and conseuqent drying of the tissues, all 

 enter into the question of winter-killing. It is true that these 

 factors along with the intense cold doubtless more often cause 

 the death of trees through stoppage of the upward water cur- 

 rent and through its removal from the cells, or cell walls, thus 

 bringing about conditions simulating those of drouth in summer, 

 yet we cannot get away from the fact that: "The capacity of 

 withstanding intense cold is a specific property of the pro- 

 toplasm of certain plants'"''****."* There is than a certain mini- 

 mum temperature below which a given variety of apples, pears, 

 or plums, cannot be expected to endure. Therefore it is a mat- 

 ter of fundamental importance to the fruit grower, first to know 

 as closely as possible the approximate zero point of a certain 

 variety and, secondly, the probable lowest range of temperature 

 of the region in which he wishes to plant, based upon recorded 

 observations extending over as many years as possible. Unfor- 

 tunately very little data of this nature is available, therefore it 

 is hoped that the following article will be of some value in this 

 respect. 



Maine being on the northern limit of commercial apple grow- 

 ing not infrequently the orchards suffer from severe low tem- 

 peratures and abrupt changes of winter weather. Prof. W. M. 

 Munson notes that in the winters of 1903-04 and 1904-05 the 

 orchards of the State experienced greater injury from condi- 

 tions of this kind than during the twenty years immediately 

 preceding. t With only one year for recovery this was followed 

 by the most disastrous winter in the history of Maine orchard- 

 ing, that of 1906-07. The amount of this injury is indicated by 

 the following, quoted from a report of a census of the injured 

 orchards carried out under the direction of Prof. E. F. Hitch- 

 ings, State Entomologist and undertaken at the instance of Hon. 

 A. "VV. Gilman, Commissioner of Agriculture : — 



* Schimper, Dr. A. F. W., Plant-Geography upon a Physiological 

 Basis, English Translation, p. 41. Clarendon Press, Oxford, (1903). 

 t Me. Agr. Exp. Sta.. Bui. 128, p. 73, 1906. 



