370 CRUCIFERJ3, OR TURNIP TRIBE. 



and "Wall-flower ; as long as the flowers remain single, however, 

 they are not valued by the florist ; but it is their tendency to 

 become double, by the development of petals in the place of 

 stamens and pistils, that gives them their richness of appearance. 

 If all the organs of fructification, however, were to undergo this 

 conversion, there would be no means of propagating any particular 

 variety or race which it might be desired to perpetuate. But 

 among the petals, a perfect stamen or two will frequently be 

 found ; and in another flower an untransformed pistil may present 

 itself; if the stigma of the latter be touched with the pollen of 

 the former, the ovules will be fertilised, and seeds will be pro- 

 duced : these, if placed in a rich soil, will have a tendency to 

 develop flowers of a similar character ; but if sown in a barren 

 place, like that which the wild plants inhabit, will probably bear 

 flowers resembling theirs. If, on the other hand, the seeds of a 

 flower departing too widely from the double form, be raised, its 

 flowers will probably be alike imperfect. It is by attention to 

 these rules, that the different races of Turnips, Radishes, &c. 

 have been preserved ; whereas if the seeds of those which do not 

 perfectly exhibit the respective characters of the races, had been 

 used for propagating them, they would all have returned in time 

 to their original common form. 



532. It is this tendency to variation under the influence of 

 cultivation, producing the effect valued by the florist in the 

 Stock and Wall-flower, which renders other plants of this order 

 valuable to Man as articles of food. There is a remarkable ten- 

 dency in many of them, to increase the amount of the fleshy 

 portion of their tissues, when abundantly supplied with nourish- 

 ment. This increase takes place in different parts, in different 

 species. Thus in the Turnip and Radish it is chiefly in the root, 

 the natural form of which is often completely changed by cultiva- 

 tion ; yet the seeds of any variety of either of these species, if 

 raised in a poor soil, will produce the tough stringy roots charac- 

 teristic of the original wild plants. In the Cabbage and Sea- 

 Kale, it is chiefly in the stems, leaf-stalks, and leaves ; as is also 

 the case in a less degree with the Turnip. The varieties of the 

 Cabbage are very numerous ; the Scotch-Kale, the Savoy, the 



