AIR DRAINAGE AS AFFECTING ACCLIMATIZATION. 29 



Mr. Macoun — I would like to give some observations as to the 

 death of plants in cold weather. 



In the Province of Behring in Canada, and also in the United States, 

 I believe one of the chief causes of death in fruit trees is the killing of 

 the trunks in winter, which we believe is due to the constant flow of cold 

 air during the winter months. We had a very good example of it in 

 Ottawa, which as you know is not in Behring Province, last year, when 

 we had a kind of winter killing which we have never had before in 

 twenty years' experience. I believe this coincides in a very large extent, 

 with the winter in Behring Province. We had a very serious kind of 

 winter, with greater cold than usual. There had been a steady flow of air 

 all through the winter ; that is much more than the average. The result 

 was a large number of apple trees which were killed in the trunk lor 

 about two feet entirely around the trunk. Now, as a rule, the form of 

 winter killing in the winter that is known as sun killing usually occurs 

 on the south and southwest side of the tree, and is due largely, we 

 believe, to the sudden changes of temperature, thawing and freezing, but 

 in these cases, I suppose, there were one hundred or one hundred and 

 fifty trees destroyed in that way, killing right around the trunk. The 

 bark and the trunk were destroyed. The trees leaved out as usual. 

 Some are living yet, but they gradually die and those that did not die 

 last year will die next year. I just wanted to give this example and give 

 one in Behring Province, where the fruit trees are killed by too much 

 air drainage. 



Mr. Souilizvick — I think it is a well-known fact that the lowering 

 of the temperature of the soil has the same effect upon plants in ap- 

 pearance at least as frost. You take the eucalyptus plant. If you have 

 a very wet cold soil the plants die. That is the result of my experi- 

 ment in Central Park now. They were planted near the house in the 

 shade and the moisture and the lowering of the temperature has caused 

 them all to die and I think it is a well-known fact and a very important 

 fact, every act of the lowering of the temperature and the excessive 

 moisture deprives the plant's leaves of the nourishment they require, and 

 they die. I think Dr. MacDougal can say a few words about that. 



Dr. MacDougal — It is true in regard to the eucalyptus plant that 

 the fatal cold in some places is between 36 and 38 degrees Fahrenheit. 

 That is to say, they freeze to death before the freezing point is reached. 

 They are not killed by cold, so that this thing you speak of is probably 

 a combination. 



Mr. Macoun — I would just like to say, as I mentioned before, that 

 we believe — although I haven't any data to prove it — that the driest part 

 of a tree is the trunk. Perhaps Dr. Hansen has some information on 

 that point. We know that near the tip there is more moisture than any 

 other part, but I believe the driest part of a tree is the trunk and this 

 constant flow of air in the winter dries out the trunk so that there is 



