PDF - Wallace Online

CREATION BY LAW 157met with. On this depends the possibility of obtainingbreeds, races, and fixed varieties of animals and plants and itis found that any one form of variation may be accumulatedby selection, without materially affecting the other charactersof the species ;each seems to vary in the one required directiononly. For example, in turnips, radishes, potatoes, and carrotsthe root or tuber varies in size, colour, form, and flavour, whilethe foliage and flowers seem to remain almost stationary ;inthe cabbage and lettuce, on the contrary, the foliage can bemodified into various forms and modes of growth, the root,flower, and fruit remaining little altered in;the cauliflowerand broccoli the flower heads vary ;in the garden pea the podonly changes. We get innumerable forms of fruit in theapple and pear, while the leaves and flowers remain almostundistinguishable the same;occurs in the gooseberry andgarden currant. Directly, however (in the very same genus),we want the flower to vary in the Kibes sanguineum, it doesso, although mere cultivation for hundreds of years has notproduced marked differences in the flowers of Eibes grossularia.When fashion demands any particular change in theform, or size, or colour of a flower, sufficient variation alwaysoccurs in the right direction, as is shown by our roses, auriculas,and geraniums ; when, as recently, ornamental leavescome into fashion, sufficient variation is found to meet thedemand, and we have zoned pelargoniums and variegatedivy, and it is discovered that a host of our commonest shrubsand herbaceous plants have taken to vary in this directionjust when we want them to do so ! This rapid variation isnot confined to old and well-known plants subjected for a longseries of generations to cultivation, but the Sikkim rhododendrons,the fuchsias, and calceolarias from the Andes, andthe pelargoniums from the Cape, are equally accommodating,and vary just when and where and how we require them.Turning to animals we find equally striking examples.If we want any special quality in any animal we have only tobreed it in sufficient quantities and watch carefully, and therequired variety is always found, and can be increased toalmost any desired extent. In sheep, we get flesh, fat, andwool in ; cows, milk in; horses, colour, strength, size, andspeed ;in poultry, we have got almost any variety of colour,