70 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



individuals become modified in the same way."* He repeats this 

 elsewhere, adding : "A new sub-variety would thus be formed without the 

 aid of natural selection." t This, we shall see in Part EL of this paper, 

 forms the basis of the true method of evolution by self-adaptation or 

 direct response of the organism to the environment. According to 

 Darwin's theory there are three sources of " indefinite variations." The 

 first is the more or less exaggerated individual differences which occur 

 under cultivation ; secondly, the insignificant individual differences- 

 which occur in wild plants ; and thirdly, the changes which appear in 

 the structure of the offspring of animals and plants which grow up under 

 changed conditions of life. 



In the third case they are purely imaginary, especially any " injurious " 

 \ariations, which Darwin thought could arise and be rigidly destroyed by 

 natural selection. 



Darwin devotes a section to " individual differences," as he calls 

 them, t as a source of varieties and species, and writes as follows : — " The 

 many slight differences which appear in the offspring from the same 

 parents, or which it may be presumed have thus arisen, from being ob- 

 served in the individuals of the same species inhabiting the same confined! 

 locality, may be called individual differences. . . . These are of the 

 highest importance to us . . . they afford materials for natural selection 

 to act on and accumulate, in the same manner as man accumulates in 

 any given direction individual differences in his domesticated productions."" 



But there is a considerable difference between individual differences 

 in nature and under cultivation. If any appear in cultivation worth 

 preserving, as, e.g., in the sizes and shapes of Carrots, or in the colours of 

 the flowers of the Sweet Pea, such might be called " exaggerated " 

 differences, as compared with what occur in nature. It is a rare thing 

 for a wild species growing for generations in the same conditions of life 

 to exhibit any differences of which a systematic botanist would take any 

 notice as furnishing materials for classifying it as a sub-variety. Thus 

 Violets may be white, or red, or purple, but such are not recognised as 

 departures from the described type. Even if all the " Shirley Poppies," 

 known to have arisen from one capsule, were wild, botanists would not 

 regard them as different species, or even varieties. 



It is a remarkable fact that with many of the commonest wild flowers, 

 often growing socially in large masses, among which one would expect 

 the chance of varieties occurring, none whatever are recognised at all ; 

 yet there are doubtless no two individuals of the same species absolutely 

 alike. The reader will at once recall the Lesser Celandine, scarlet 

 field Poppy the origin of the " Shirleys," Daisy, Common Heath and 

 Ling, Foxglove, Bracken, &o. No varieties are recorded in Hooker's 

 " Student's Flora " of any of these abundant species, with the exception of 

 the first, in which slight differences in the petioles occur. 



Some botanists have taken up the study of individual differences to 

 endeavour to trace out any laws of variations arising from them. 



It has been said, for example, that "if we may judge from some 



* Origin Ac, p. 106. 



t OrtQin Ac, p. 72. and An, and PI under Dom. ii. p. 271. 

 X Origin Ac, p. B4. 



