DAE\YIN AND BOTANY 359 



injurious. The phenomena do not now, however, appear to have as 

 important a relation to evolution as they were formerly supposed to 

 have, and Darwin later expressed regret that he had not given more 

 attention to the processes of self-fertilization. 



His interest in showing that cross-fertilization was beneficial led 

 him to closely investigate the various structural features of flowers 

 which necessitate this process to a greater or less degree, such as dioecism, 

 monoecism, polygamy and heterostyly ; his observations and speculations 

 are presented in the volume entitled " Different Forms of Flowers and 

 Plants of the Same Species," published in 1877. He records that 

 making out the meaning of heterostyled flowers gave him very great 

 pleasure. A chapter of the book is devoted to cleistogamic flowers, 

 which are necessarily self-fertilized and produce seed abundantly. This 

 work is largely a revision and rearrangement of several papers previously 

 published in the Journal of the Linncran Society. 



"The Variation of Animals and Plants under Domestication," 

 Darwin's largest work, appeared in 1868, published in two volumes. As 

 bearing on this topic he had studied, among plants for many years, the 

 cereal grains, garden vegetables, edible fruits, ornamental trees and 

 ornamental flowers. In the preface he again discusses natural selection 

 and defines it as "This preservation, during the battle for life of 

 varieties which possess any advantage in structure, constitution or 

 instinct," noting that Herbert Spencer had well termed the same process 

 " The Survival of the Fittest." But the bulk of the work is given to 

 the consideration of selection by man — artificial selection, by which races 

 useful to us, economically or esthetically, have been preserved and 

 modified, some of them having originated in very remote times and been 

 taken advantage of by uncivilized man. A chapter is devoted to the 

 phenomena of bud-variation, in which many cases of branches of plants 

 different in one respect or another from other branches on the same 

 plant are described in detail. Many of these have been taken advan- 

 tage of by horticulturists for the propagation of valuable races. He did 

 not reach any definite conclusion as to the cause of these interesting 

 occurrences ; but recently acquired knowledge of mutation seems to indi- 

 cate that they are of that category, differing from seminal mutations in 

 that a cell in the axil of a leaf is affected rather than a germ-cell. In 

 these volumes we find Darwin's most detailed discussion of heredity of 

 variability and of hybridism and the last chapter outlines his provisional 

 hypothesis of Pangenesis, an ingenious supposition, applying to living 

 matter the general features of the atomic theory, with an additional 

 inherent power of reproduction of the atoms or "gemmules" as he 

 termed the hypothetical ultimate particles. 



The movements of plants and of their various organs were also 

 studied by Darwin for many years. His first essay on this topic 



