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IV. Studies on Transpiration in High-moor 



Plants. 



By P. Boysen- Jensen. 



The appearance of high-moors is in general very homogeneous. 

 The number of plant-species is small and it is the same plants that 

 are found on nearly all the high-moors. In "Maglemose", a high- 

 moor in the wood of Gribskov, where the following investigations 

 were carried out , the predominant plants are Eriophorum vaginatum, 

 Calluna vulgaris, Vaccinium uliginosum, Vaccinium Vitis idaea, 

 Empetrum nigrum, Betula sp. and Picea excelsa. 



The soil in the high-moors is very compact and wet. The 

 oxygen content is therefore small; the soil is cold and acts on the 

 plants as a dry soil. It is obvious that the majority of the plants 

 on the high -moors are protected against rapid transpiration in one 

 way or another. The cricoid type of leaves is represented by Calluna 

 and Empetrum, the pinoid type by Picea, and other plants, as 

 Vaccinium Vitis Idaea, Andromeda and Oxy coccus possess coriace- 

 ous leaves. But besides these xeromorphic plants others can he 

 found, in which the leaves are not protected from desiccation in 

 any way: for instance Betula, Rubus Chamaemorus, Cornus suecica, 

 Vaccinium Myrtillus etc. From this it appears that a xeromorphic 

 leaf structure is not absolutely necessary for plants growing on 

 high-moors and the question arises, of what importance the xero- 

 morphy is for the high-moor plants possessing it. 



An attempt at solving this question will have to begin with 

 a comparison of the transpiration from xeromorphic and non-xero- 

 morphic leaves to see what influence the xeromorphy has on the 

 transpiration. It is such a comparison that I have carried out. In 

 several series of experiments I have determined the amount of water 

 that is transpired pr. 100 cm 2 leaf area, pr. hour in different plants. 

 After some preliminary investigations I chose the following 4 plants 

 for my experiments, 2 with xeromorphic leaves, viz. Empetrum and 

 Vaccinium Vitis idaea and 2 with non xeromorphic leaves, viz. 

 Vaccinium uliginosum and Betula. In these plants the rate of 

 transpiration was determined at different times of the year, but 

 every time under the same external conditions. 



