DAKWINISM 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 as 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. The 

 flowers and seeds of all these plants have remained nearly 

 stationary, because no attempt has been made to accumulate 

 the slight variations that no doubt occui' in them. 



If now we turn to another set of plants, the turnips, 

 radishes, carrots, and potatoes, we find that the roots or under- 

 ground tubers have been wonderfully enlarged and improved, 

 and also altered in shape and colour, while the stems, leaves, 

 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 important to notice that while 

 all these plants have undergone cultivation in a great variety 

 of soils and climates, mth different manures and under 

 different systems, yet the flowers have remained but little 

 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 are con- 

 tinually occurring. When, however, a great amount of modifi- 

 cation has been effected in one country, change to another 

 country produces a decided effect. Thus it has been found 

 that some of the numerous varieties of maize produced and 

 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.^ In all 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. 



^ Darwin, Animals and Plants under Domestication, vol. i. p. 322. 



