Caryophyllaceæ. 281 



raun belonged to those which had the least transpiration, 

 and the slightest growth. The result does not appear to have 

 been very conclusive, but he says that, on the whole, the 

 Arctic plants which were investigated had only slight trans- 

 piration, compared with plants from more southern regions. 

 This must, beyond doubt, be due to the atmospheric humi- 

 dity, which is certainly greater during the vegetative period 

 than outside it. The leaf-structure of herbaceous plants 

 agrees well with the humid air, the fogs and the abundant 

 water-contents of the soil. As regards the physiological 

 dryness in Arctic countries certainly too much has been said. 

 Thorild Wulff generalized in too high a degree in saying, 

 that the Arctic flora "is of a decidedly xerophytic type," 

 although this is true only of the woody plants. 



The above-mentioned conditions pertaining to the 

 habitat also explain, at any rate some of the morphological 

 conditions, e. g., that in so many cases adventitious roots 

 are developed; that runners are formed may be due to the 

 fact, that the low temperature has altered the growth-direc- 

 tion of the shoots (Psychrokliny: Vöchting, 1898; Lidforss, 

 1903), the moisture, perhaps in connection with the pres- 

 sure of the snow, having favorised a development of adven- 

 titious roots. On the other hand, it must be the cold and 

 desiccating winds which cause the frequently -occurring 

 pulvinate growth; the shoots are arrested in their growth, 

 and the branches become short and thick-set. 



That the buds are open and that bud-scales are absent, 

 I regard as a generic character. This results in conditions 

 favourable to the development of the pulvinate habit, espe- 

 cially when the plants are covered with a layer of snow, 

 which lasts throughout the winter; many leaves must be 

 able to keep green for a long time, at all events until the 

 snow has united, and the youngest leaves are ready for 



