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For plants growing on hard soil I have found the following 

 values for the relative transpiration. 



Width of the Relative 

 stomata Transpiration 



Senecio silvaticus 2 42 



Populus tremula 2 27 



Fagus silvatica 2 25 



In the plants investigated the rate of transpiration is therefore 

 2 — 3 times so great as for high-moor plants. 



The result of the experiments is as follow: The transpiration 

 in high-moor plants is less than in plants growing on hard soil. The 

 difference between the four moor-plants is rather small. 



Now when we again ask what importance the xeromorphy 

 has in regulating the transpiration of the high-moor plants where 

 it is present the answer seems to be that the xeromorphy either 

 is of no significance or at any rate of very little. Yet it is too early 

 to pronounce a decision on this point. As mentioned above the 

 transpiration is either cuticular or stomatal. It might then be pos- 

 sible that the effect of the xeromorphic structure in regulating the 

 transpiration is counteracted by the opening or closing of the sto- 

 mata. We must therefore consider the stomata and their importance 

 for the high-moor plants. 



In general it may be said that the influence of the stomata 

 on the transpiration has been very little investigated. Lloyd 

 (1908) has found that the significance of the stomata is very little. 

 On the other hand experiments of Renner (1910), Darwin 

 and P e r t z (1911) and Darwin (1916) show that the transpira- 

 tion is increased by the opening of the stomata. I have found the 

 same in my experiments. 



In the high-moor plants I have tried to measure the transpira- 

 tion with different degrees of widths of the stomata. The width 

 was estimated with alcohol and xylol in the manner described above. 

 It was rather difficult to get plants showing the different stages 

 of opening of the stomata. In Vaccinium Vitis idaea the width 0 

 was produced by darkening the plants ; the widths 1 and 2 can be 

 found in nature. In Betula the width 0 and 1 can easily be found, 

 on the trees on the high-moor, leaves with the width 2 was found 

 in young trees on hard soil. In Vaccinium uliginosum the stages Ö 

 and 1 can also be found in nature ; once I have found the width 2. 



The results of these experiments are given in table 3. It may 

 be seen that the transpiration from leaves with open stomata is 



