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Show 86 DARWINISM CHAP. which the whole mode of growth has been altered, numerous little heads of leaves being produced on the stem. In other varieties the ribs of the leaves are thickened so a.. to become themselves a culinary vegetable; while, in the Kohlrabi, the stem grows into a turnip-like mass just above ground. Now all these extraordinarily distinct plants come from one original species which still grows wild on our coasts; and it must have varied in all these directions, otherwise variations could not have been accumulated to the extent we now see them. Tho flowers and seeds of all these plants have remained nearly stationary, because no attempt has been made to accumulate tho slight variations that no doubt occur in them. If now we turn to another set of plants, the turnips, radishes, carrots, and potatoes, we find that the roots or underground tubers have been wonderfully enlarged and improved, and also altered in shape and colour, whlle the stems, lca,vc., flowers, and fruits have remained almost unchanged. In the various kinds of peas and beans it is the pod or fruit and the seed that has been subjected to selection, and therefore greatly modified; and it is here very importa.nt to notice that while all these plants have undergone cultivation in a great variety of soils and climates, with different manures and under different systems, yet the flowers have remained but li LLle altered, those of the broad bean, the scarlet-runner, and the garden-pea, being nearly the same in all the varieties. This shows us how little change is produced by mere cultivation, or even by variety of soil and climate, if there is no selection to preserve and accumulate the small variations that arc continually occurring. When, however, a great amount of mo<li!-ication has been effected in one country, change to anotl1cr country produces a decided effect. Thus it has been fonncl that some of the numerous varieties of maize produced HJHl cultivated in the United States change considerably, not only in their size and colour, but even in the shape of the seed when grown for a few successive years in Germany.l In an our cultivated fruit trees the fruits vary immensely in shape, size, colour, flavour, time of ripening, and other qualities, while the leaves and flowers usually differ so little that they are hardly distinguishable except to a very close observer. 1 Darwin, Animals and Plants undet· Domestication, vol. i. p. 322. IV IATION UNDER DOMESTICATION 87 Vctriations of Apples a11d of Jlfelons. The most remarkable vn,rieties arc afforded hy the apple ~nd the. melon, and some account of these will he giv n as Illustt:at111g the effects of slight variation. accumulated hy selectiOn. All our apples arc known to have descended from tho common crab of our hedges (Pyrus malus), and from this at lea,st .a. thou a.nd . distinct varieties have been produced. The c drflcr. grea.tly m the size a.nd form of the fruit, in its colour, aJHlm the texture of tho skin. They further differ in the ti~c of ripening, in their flavour, and in their keeping propcrt~cs; but app~c trees a,l~o . differ in many other ways. The fohage of the drffercnt vanet10s can often be di tin()'mshed ?Y pecu.lia.rities. of form and col?ur, and it varies considerably I~ the tm1c ~f ~ts appearance; m some hardly a leaf appear. till the tree IS m full bloom, while others produce their leaves so early as almo t to hide the flowers. The flovv-ers differ in size and colour, and in one case in structure also, that of the St. Valery apple having a double calyx with ten divisions and fourteen style. with oblique stigmas, but without stamc~s or corolla. The flowers, therefore, have to be fertilised with the pollen from other varieties in order to produce fruit. Tho pips or seeds differ also in sha.pc, size and colour · some varieties arc liable to canker more th~n others while tho Winter Ma.jetin and one or two others have the ;tran()'e constitutional peculiarity of never being attacked by theb mealy bug even when a.ll the other trees in the same orchard arc infested with it. All the cucumbers and gourds vary immensely bnt the melon (Cucumis melo) exceeds them all. A French' botani t M. N audin, devoted six years to their study. He found that previous bot~nists had described thirty distinct species, as they t~ought,. whi~h we~e re~lly only varieties of melons. They differ ch10fty m their frmts, but also very much in foliage and mode of growth. Some melons are only as large as small plums, others weigh as much as sixty-six pounds. One variety has a scarlet fruit. Another is not more than an inch in diameter, but sometimes more than a yard in len()'th twistin()' about in all directions like a serpent. Some b m~lons ar~ exactly like cucumbers; and an Algerian variety, when ripe, |