Caryophyllaceæ. 281 



пит belonged to those which had the least transpiration, 

 and the sUghtest growth. The result does not appear to haA^e 

 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 (Psychrokhny: 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 coA^ered 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 melted, and the youngest leaves are ready for 



