1889.] BOTANICAL GAZETTE. 219 



action was going on vigorously at the time. The experiment 

 was continued for ten days, but without any very definite results. 

 The maximum of temperature alternated rather irregularly 

 between the live and dead wood, and did not seem to give 

 any uniform results. The causes of these rapid_ fluctuations 

 are not so easy to understand, yet I think that it is extremely 

 doubtful whether the metabolic processes involved generate 

 sufficient heat to influence the ordinary thermometer. 



We have seen above that considerable difference was 

 found between evergreens and deciduous trees like the oak. 

 To see if this same difference was apparent between ever- 

 green and deciduous conifers, an experiment was tried with 

 the pine (Pinus sylvestris) and the European larch (Lanx 

 Europcea). The results obtained are shown in B, plate xvin. 

 They indicate that the temperature of the larch and oak 

 were very nearly the same. As a general rule the tempera- 

 ture of the larch was above the pine during the greater part 

 of the day, the reverse being true for the night and early 

 morning. There is not anv very great difference in the 

 structure of the wood of the larch and pine, so that this 

 difference can not be attributable to this cause. It seems to 



lie in some other direction. 



Comparative observations were made with the pine, larch, 

 oak, poplar, and outside air, and in all cases the temperature 

 of the pine was found to be considerably lower than any ot 

 the remainder, with the exception mentioned. lo what, 

 then, is this lower temperature due? Presumably the thick 

 coating of foliage on the pine exerts a considerable influence 

 upon it, as it would seem to have a tendency to prevent ab- 

 sorption of heat by the trunk, and would very likely interfere 



with radiation to some extent. m « , . 



In order to see what influence the foliage had upon the 

 temperature of the trunk, the following experiment was 

 made: Two balsam firs (Abies balsamea) were chosen, that 

 were as nearly like each other as possible, and the tempera- 

 tures of thei/trunks were compared with each other tor a 

 time, to see if any material difference existed between the 

 individual trees. The foliage of this tree presents a com- 

 pact surface, and was thus better adapted for the experiment 

 than the pine. After a short period of comparison between 

 the two trees, one of them was stripped of its foliage foi a 

 distance of several feet above the thermometer, and compai- 

 ative readings were then taken, to see what influence denuda- 

 tion of foliage exerted upon the temperature of the trunk. 



