ON THE SUBJECTIVE CAUSES OF EVOLUTION AS 

 ILLUSTRATED BY THE GEOGRAPHICAL DISTRI- 

 BUTION OF PLANTS. 



By Professor Guthrie, LL.B. 



[Read 25th April, 1888.] 



INTRODUCTION. 



When a seed germinates the character of the plant that will be 

 evolved depends both on the nature of the seed and on its environment. 



The first may be called the subjective^ the latter the objective cause 

 of the plant's ultimate form. 



Soil, moisture, light, temperature, as well as man's direct inter- 

 ference in training and pruning, may make all the difference between 

 a stunted pot plant of a few inches high and a magnificent forest 

 tree. But whatever differences may thus be objectively produced 

 there are certain unchangeable subjective characteristics due to the 

 nature of the seed itself which cannot be altered. No cultivation 

 for example will evolve a fir tree from an acorn. 



It is now generally believed, and will here be assumed, that existing 

 species of plants and animals have been evolved from dissimilar 

 pre-existing species, and the question arises to what extent the forms 

 of existing species are due to subjective as well as objective causes, 

 that is to say to what extent the forms of existing species are due 

 to the subjective tendency or capability of the ancestral species from 

 which they have been evolved of varying in what may be called 

 'prescribed ways, or whether there is no such prescribed capability 

 or tendency and whether evolution is due to environment only. 



Darwin's theory of evolution by natural selection seems to have 

 left this question open. His own views seem to have undergone a 

 change between the dates of the publication of the first and last 

 edition of the " Origin of Species." At the date of his first edition 

 (1859) he seems to. have been disposed to account for evolution almost 

 entirely on objective grounds, whereas at the date of his last edition 

 (1886) he clearly laid more stress on subjective causes of evolution. 



It is true that the only subjective element of evolution he expressly 



