OiLvp. XXIII. CONDITIONS OF LIFE. 277 



a thin and elongated neck, stiff and lank hair, are the chief 

 characteristics. The change in the nature of the hair is sup- 

 posed to be caused by the dryness of the atmosphere. If im- 

 migration into the United States were now stopped, who can 

 say that the character of the whole people would not be greatly 

 modified in the course of two or three thousand years ? 



^ The direct and definite action of changed conditions, in contradis- 

 tinction to the accumulation of indefinite variations, seems to me so 

 important that I will give a large additional body of miscellaneous facts. 

 With plants, a considerable change of climate sometimes produces a con- 

 spicuous result. I have given in detail in the ninth chapter the most 

 remarkable case known to me, namely, that in Germany several varieties 

 of maize brought from the hotter parts of America were transformed 

 in the course of only two or three generations. Dr. Falconer informs 

 me that he has seen the English Eibston-pippin apple, a Himalayan 

 oak; Prunus and Pyrus, all assume in the hotter parts of India a fastigate 

 or pyramidal habit; and this fact is the more interesting, as a Chinese 

 tropical species of Pyrus naturally has this habit of growth. Although 

 in these cases the changed manner of growth seems to have been 

 directly caused by the great heat, we know that many fastigate trees have 

 originated in their temperate homes. In the Botanic Gardens of Ceylon 

 the apple-tree 22 " sends out numerous runners under ground, which con- 

 tinually rise into small stems, and form a growth around the parent-tree." 

 The varieties of the cabbage which produce heads in Europe fail to do so 

 in certain tropical countries. 23 The Rhododendron ciliatum produced at 

 Kew flowers so much larger and paler-coloured than those which it bears 

 on its native Himalayan mountain, that Dr. Hooker 24 would hardly have 

 recognised the species by the flowers alone. Many similar facts with 

 respect to the colour and size of flowers could be given. 



The experiments of Vilmorin and Buckman on carrots and parsnips 

 prove that abundant nutriment produces a definite and inheritable effect 

 on the so-called roots, with scarcely any change in other parts of the plant. 

 Alum directly influences the colour of the flowers of the Hydrangea. 25 

 Dryness seems generally to favour the hairyness or villosity of plants. 

 Gartner found that hybrid Verbascums became extremely woolly when 

 grown in pots. Mr. Masters, on the other hand, states that the Opuntia 

 leucotricha "is well clothed with beautiful white hairs when grown in a 

 " damp heat ; but in a dry heat exhibits none of this peculiarity!" 26 Slight 

 variations of many kinds, not worth specifying in detail, are retained only as 



22 'Ceylon,' by Sir J. E. Tennent, 25< Journal ofHort.Soc.,' vol. i. p. 160. 

 vol. i. 1859, p. 89. 20 See Lecoq, on the Viilosity of 



23 Godron, ' De l'Espece,' torn. ii. p. Plants, ' Geograph. Bot.,' torn. iii. pp. 

 52. 287, 291 ; Gartner, < Bastarderz.,' s. 2G1 ; 



- 4 'Journal of Horticultural Soc.,' Mr. Masters, on the Opuntia, in ' Gard, 



vol. vii., 1852, p. 117. Chronicle,' 1846, p. 444. 



