2i8 botanical gazette. [September, 



the winter months. During the cold days in the early part 

 of February, in which the thermometer fell to -22 C, we 

 find that the interior of the tree registered only 5 degrees 



higher than this. 



To see if there was any material difference between con- 

 ifers and deciduous trees, an experiment was made with a 

 Scotch pine (Pinus sylvestris), and a white oak (Quercus 

 alba). The trees selected were of nearly the same diameter, 

 and all other factors were considered, to equalize, as far as 

 possible, the conditions of the experiment. By reference to 

 A, plate xviii, it will be seen that in no case (where conditions 

 w r ere favorable for the experiment) was the temperature of 

 the pine as high as that of the oak, with the exception of 

 the early observations in the day. As a general rule, the 

 observations from 7 to 10 a. m. indicated a higher tempera- 

 ture in the pine than in the oak. This is due to the slower 

 radiation of the pine. It is noticeable that the temperature 

 of the oak falls more rapidly than the pine, late in the afternoon, 

 showing that it radiates the heat absorbed during the warmer 

 portions of the day quicker than the pine, which is clothed 

 with evergreen foliage. 



Prof. Prentiss states that conifers have a higher specific 

 heat than deciduous trees in winter. 1 He uses the term 

 specific heat, not in its physical sense, but as meaning the 

 heat evolved by metabolic processes. From the observa- 

 tions made here we have been unable to arrive at similar 

 results. The temperature of the pine we found to be lower 

 than that of the oak at all times except during the latter 

 part of the night and early morning, and the chemical changes 

 occurring in the stem at this season of the year are probably 

 so slight that radiation would carry off the heat about as fast 

 as it was produced. The period of observation for this ex- 

 periment extended over the middle of March, with the 

 temperature ranging high for this season of the year, but as 

 yet little or no change had taken place in the interior struc- 

 ture of the tree. To see if heat evolved by chemical changes 

 in the tree would be sensible to a thermometer, a compari- 

 son was instituted later in April between dead and live 

 timber. The tree selected was a very favorable one for the 

 experiment, inasmuch as it had one large dead branch, with 

 bark intact, while the remaining branch was a vigorous 

 growth. This apple tree was taken for the experiment at a 

 time when the buds were quite well started, so that chemical 



1 2d Kept. Cornell Univ. Exp. Stat. ('82 and '83), page 42. 





