140 LEAVES OF CONIFERS [CH. 



which we cannot directly refer to the action of the en- 

 vironment. 



Those variations which, in a given situation and 

 season, are dangerous to the life of the plant, may be 

 exterminated by the rigour of the environment ; whereas 

 those variations which make for adapting the plant a 

 little more to the conditions prevailing at the time, are 

 apt to be preserved. A race of plants may thus be 

 produced more adapted to the environment than ever 

 before. 



This is the gist of the argument for Natural Selection, 

 and it certainly promises a better explanation of the 

 following cases than any other hypothesis. Indeed the 

 only alternative is to appeal to unsubstantiated hypotheses 

 which not only offer no explanation of the phenomena 

 at all, but which lead us into a nightmare of illusions 

 quite outside the evidence of Natural Science. 



That the narrow leathery leaves of Conifers, such as 

 Pines, Firs, Cedars, &c., are adapted to the peculiar con- 

 ditions of their natural habitats can hardly be doubted. 

 Being evergreen, they are peculiarly exposed to two dan- 

 gers in their Alpine homes : namely to being intensely 

 heated and illuminated by the direct solar rays, in very 

 clear weather and at periods when the roots are still in 

 frozen soil and inactive, and, secondly, to the danger of 

 accumulations of large and weighty coverings of snow 

 during the winter. An adaptation which appears to meet 

 the first danger seems to be their low transpiratory activity. 

 They have a very thick protective cuticle and expose but 

 small surfaces to the air ; the stomata are few and sunk in 

 grooves ; and their vascular supply is minute. In accord- 

 ance with this we find that they transpire far less water 

 than do similar areas of the broad thin leaves of Dicoty- 

 ledons, as shown by the following determinations made by 



