— 152 — 



2 — 3 times as great as when the stomata are closed. But further 

 it may be seen that the transpiration in Vaccinium Vitis idaea is 

 less than in Vaccinium uliginosum and Betula, when the width of 

 the stomata and the surrounding conditions are the same. On the 

 other hand it may be concluded that when the transpiration is 

 about the same in the three plants, as was found in the experiments 

 described above, the width of the stomata is different. That was 

 indeed the case as could be shovn. 



Table 3. Relative transpiration with different widths of the stomata. 





0 



1 



2 



Vacc. Vit. idaea . 



. 5 



13 



18 



Vacc. uliginos. . . . 



13 



(16) 



22 



Betula 



13 



19 



35 



The result of these experiments is given in table 4 where the 

 width of the stomata in the different experiments is stated. When 

 only a part of the stomata are open, the size of this part is indicated 

 (Yio : 2 means that 1 / 10 of the leaf surface has the width 2). 



It will be seen that the width of the stomata was about 1 in Vac- 

 cinium Vitis idaea; in Vaccinium uliginosum and Betula the stomata 

 were either closed or at any rate only open on isolated spots*). 



Table 4. The width of the stomata. 



1914 





28/ 

 /6 



5 / 7 



23/ 



3 % 



% 







Vacc. Vit. idaea 



1 



1 



1 



1 



l-(2) 



1 









trace 



trace 

 of 2 





l-(2) 





J:2 







Betula 



0 



trace 

 of 1 



trace 

 of 1 



1 



1 



trace 

 of 2 







1915 



6 / 6 



13/ 

 /6 



2 % 



21 / 7 



25/ 



15 / 8 



29/ 

 18 



12 / 9 



Vacc. Vit. idaea 



(0)-l 



0—] 



0—1 



1 



1 



1 



1—2 



(0)-l 



Vacc. uligin 



0 



trace 



0 



trace 

 of 2 



trace 

 of 2 



trace 

 of 2 



0 



trace 

 of 1 



Betula 



0 



0 



0—1 



trace 

 of 1 



trace 

 of 2 



|:1 



trace 

 of 1 



trace 

 of 1 



*) In young plants of Betula the stomata are perhaps more open than 

 in the trees. The leaves used for my experiments were taken from trees. 



