406 ON THE SUPPOSED BOTANICAL PROOFS OF THE 



proved from the fact that our cherry has become an evergreen in 

 Ceylon. 



Such are Detmer's opinions, and every one will agree with him 

 in believing that the periodical change of leaf in temperate climates 

 has been produced in relation to the recurring alternation of summer 

 and winter. This is certainly the case, and it cannot be doubted 

 that the character has become fixed by heredity. Where, however, 

 is the proof that this hereditary character has been produced by the 

 direct influence of climate ? What right have we to look upon 

 the hereditary appearance of the character as an after-effect of the 

 direct influence exerted by changes of temperature upon previous 

 generations ? Such an opinion derives but little support from the 

 previously described experiments upon after-effect, which showed 

 that these phenomena were never hereditary. 



It appears to me that there are certain points in this change of 

 leaf and its accompanying phenomena, which distinctly indicate 

 that natural selection has been at work. Can Detmer imagine that 

 the brown scales which form the characteristic protective covering 

 of winter buds have been produced by the direct action of the cold? 

 If, however, the peculiar structure of these buds is to be referred to 

 the specific constitution of the individual rather than to the direct 

 effects of climate, would it be so very improbable for their physio- 

 logical peculiarity of lying dormant for several months to have 

 been developed simultaneously with the structure, by the operation 

 of natural selection? And if this explanation be correct, we can at 

 once see why the character has become hereditary, for natural 

 selection w r orks upon variations of the germ-plasm, and these are 

 transferred from one generation to another with the germ-plasm 

 itself. 



But Detmer attempts to establish the converse conclusion, and 

 he argues that the hereditary change of leaf has been abandoned 

 under the long-continued effect of changed climatic conditions ; 

 but this opinion is based upon the single instance of the alteration 

 in the habit of the European cherry in Ceylon. If it were proved 

 that our cherry, grown from seed in Ceylon and propagated by 

 seed for several generations, became evergreen gradually and not 

 suddenly in the first generation: if, under such circumstances, it 

 came to retain its leaves in the autumn and ceased to produce the 

 dormant winter buds: then indeed the transmission of acquired 



