34:4 CILINAEY PLANTS. Chap. IX. 



are the parents, now all commingled together, of the various 

 cultivated kinds. ]n the same manner as we have often seen with 

 domesticated animals, the sujiposed multiple origin of the cabbage 

 throws no light on the characteristic dilferences between the 

 cultivated forms. If our cabbages are the descendants of three 

 or four distinct species, every trace of any sterility which may 

 originally have existed between them is now lost, for none of the 

 varieties can be kept distinct without scrupulous care to prevent 

 intercrossing. 



The other cultivated forms of the genus Brassica are descended, 

 according to the view adopted by Godron and Metzger,^* from two 

 species, B. napus and rapt ; but according to other botanists from 

 three species ; whilst others again strongly suspect that all these 

 forms, both wild and cultivated, ought to be ranked as a single 

 species. Brassica napus has given rise to two large groups, namely, 

 Swedish turnips (believed to be of hybrid origin) " and Colzas, 

 the seeds of which yield oil. Brassica rapa (of Koch) has also 

 given rise to two races, namely, common turnips and the oil-giving 

 rape. The evidence is unusually clear that these latter plants, 

 though so different in external appearance, belong to the same 

 species; for the turnip has been observed by Koch and Godron 

 to lose its thick roots in uncultivated soil ; and when rape and 

 turnips are sown together they cross to such a degree that 

 scarcely a .single plant comes true." Metzger by culture converted 

 the biennial or winter rape into the annual or summer rape, — 

 varieties which have been thought by some authors to be specifically 

 distinct.'* 



In the production of large, fleshy, turnip-like stems, we have 

 a case of analogous variation in three forms which are generally 

 considered as distinct .species. But scarcely any modification seems 

 so easily acquired as a succulent enlargement of the stem or root — 

 that is, a store of nutriment laid up for the plant's own future use. 

 We see this in our radishes, beet, and in the less generally known 

 " turnip-rooted '' celery, and in the finocchio, or Italian variety of the 

 common fennel. Mr. Buckman has lately proved by his interesting 

 experiments how quickly the roots of the wild parsnip can be 

 enlarged, as Vilmorin formerly proved in the case of the carrot.'^ 



" Godron, ' De I'Espfece,' torn. ii. p. " ' Gardener's Chron. and Agricult. 



o4; Metzger, ' Kohlarten,' s. 10. Gazette,' 1865, p. 730. 



'^ 'Gardener's Chron. and .\gricult. '* Metzger, 'Kohlarten,' s. 51. 



Gazette,' 1856, p. 729. See, more " These experiments by Vilmorin 



especially, ibid., 1868, p. 275: the have been quoted by many writers, 



writer asserts that he planted a variety An eminent botanist. Prof. Decaisue, 



of cabbage (5. ofc/-aft?a) close to turnips has lately expressed doubts on the 



(i?. rajjo) and raised from the crossed subject from his own negative results, 



seedlings true Swedish turnips. These but these cannot be vahie.i equally 



latter plants ought, therefore, to be with positive results. On the other 



classed with cabbages or turnips, and hand, M. Carri&re has lately stated 



uot under .6. »k«>t/'is. ('Card. Chronicle,' 1865, p. 1154), 



