S6 NATURAL SELECTION FROM 



Selection becomes a factor of enormous impor- 

 tance; for the species that survive determine, 

 within limits, the species to be produced. 



NON-UTILITY IN THE EVOLUTION OF 

 GYMNOSPERMS 



A general illustration of this point of view may- 

 be taken from the phylogenetic relationships 

 among Gymnosperms. This ancient group 

 stands among plants as one of remarkable rigid- 

 ity. Land plants should be more plastic than 

 land animals, for they must remain fixed in a 

 given environment, while animals can shift their 

 environment when the pressure of change comes. 

 A striking contrast between the taxonomic char- 

 acters used by zoologists and those used by bot- 

 anists is brought out here. Among botanists, the 

 taxonomic characters in most general use are 

 those that respond with least promptness or not 

 at all to changing environment; while among 

 zoologists, as I am informed, the taxonomic char- 

 acters in most general use largely fall in the cat- 

 egory of so-called " adaptation " characters, 

 which had far better be called " response " char- 

 acters. For this very reason, I can easily imag- 

 ine that there should be more supporters of Nat- 

 ural Selection among zoologists than among bot- 

 anists. 



Be this as it may, Gymnosperms seem to be 

 about the least plastic of land plants, certainly 

 the least plastic of any great group. Even the 



