EVEEGREEN TREES IN WINTER. 329 



It is probable, though I have not made any accurate 

 observations respecting it, that stomatal transpiration is, in 

 this period at least, greatly checked ; but that a hermetic 

 closure of the stomata does exist in these plants, as observed 

 by Stahr^ and Lidforss"^ in most winter-green leaves, is 

 doubtful judging from the results of the cobalt-test. 



If, on the other hand, we compare the transpiration in 

 each plant observed in March, we obtain the following arrange- 

 ment (conf. Table VIII) :— 



Querc7ts 3.92 



Piftofiporum 2.1.5 



lllicium 2.11 



Teriistrœmîa 1.9.3 



Thea 1.00 



Eriohotrya 2.14 



Photinia 1.22 



Fatsia 2.63 



Dapliniphyllum 1.34 



Here the differences between them are greater, and the 

 ratio ranges between 1 and 2.63 {Quercus being excepted). 

 It may thus be seen that, in the coldest part of winter, the 

 transpiration in various evergreen trees becomes approximate in 

 amount, but diverges widely as the environment becomes favour- 

 able to transpiration. The explanation of this phenomenon is 

 not easily found, since the factors which act upon plants are 

 complex ; but it is obvious that their influence varies with 

 different species. 



This variability of transpiration becomes more apparent 

 when the change of transpiration of each individual is traced 



1) Stahl, I.e. 



2) Lid for ss, I.e. 



