134 HISTORY OF BOTANY 



reading a short paper by Asa Gray, published in 1858. 

 He sent me some seeds, and on raising some plants I was 

 so much fascinated and perplexed by the revolving 

 movements of the tendrils and stems, which movements 

 are really very simple, though appearing at first sight 

 very complex, that I procured various other kinds of 

 climbing plants and studied the whole subject. . . . 

 Some of the adaptations displayed by climbing plants 

 are as beautiful as those of orchids for ensuring cross 

 fertilisation/ 



" In the midst of all this amount of work, remarkable 

 alike for its variety and its importance, among plants, 

 the animal kingdom was by no means neglected. A 

 large moiety of The Variation of Animals and Plants 

 Under Domestication (1868), which contains pieces justi- 

 ficatives of the first chapter of the Origin, is devoted to 

 domestic animals, and the hypothesis of ' pangenesis ' 

 propounded in the second volume applies to the whole 

 living world. In the Origin Darwin throws out some 

 suggestions as to the causes of variation, but he takes 

 heredity, as it is manifested by individual organisms, for 

 granted, as an ultimate fact ; pangenesis is an attempt 

 to account for the phenomena of heredity in the organism, 

 on the assumption that the physiological units of which 

 the organism is composed give off gemmules, which in 

 virtue of heredity, tend to reproduce the unit from which 

 they are derived/' (Huxley.) 



Darwin's subsequent works on such subjects as the 

 Descent of Man, the Expression of the Emotions, etc., 

 do not concern us here, though the former book created 

 well-nigh as great a sensation as the Origin itself. 



In the beginning of 1882 Darwin's health, always feeble, 

 began to give way very rapidly, and he breathed his last 

 on April igth of that year, at the age of seventy-three. 



As I would like you to carry away with you from 

 these lectures not only some conception of the achieve- 

 ments of the leaders in botanical thought but also a 



