Chap. IX. CABBAGES. 325 



raised by me were not nearly so constant in character as any common 

 cabbage. 



Although most of the kinds keep true if carefully preserved from 

 crossing, yet the seed-beds must be yearly examined, and a few seedlings 

 are generally found false; but even in this case the force of inheritance 

 is shown, for, as Metzger has remarked 69 when speaking of Brussel-sprouts, 

 the variations generally keep to their " unter art," or main race. But in 

 order that any kind may be truly propagated there must be no great 

 change in the conditions of life ; thus cabbages will not form heads in hot 

 countries, and the same thing has been observed with an English variety 

 grown during an extremely warm and damp autumn near Paris/ 

 Extremely poor soil also affects the characters of certain varieties. 



Most authors believe that all the races are descended from the wild 

 cabbage found on the western shores of Europe ; but Alph. De Candolle 71 

 forcibly argues on historical and other grounds that it is more probable 

 that two or three closely allied forms, generally ranked as distinct species, 

 still living in the Mediterranean region, are the parents, now all com- 

 mingled together, of the various cultivated kinds. In the same manner 

 as we have often seen with domesticated animals, the supposed multiple 

 origin of the cabbage throws no light on the characteristic differences 

 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 inter- 

 crossing. 



The other cultivated forms of the genus Brassica are descended, 

 according to the view adopted by Godron and Metzger/ 2 from two species, 

 B. napus and rapa ; 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 (by some 

 believed to be of hybrid origin) 73 and Colzas, the seeds of which yield 

 oil. Brassica rapa (of Koch) has also given rise to two races, namely, 

 j 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. 74 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. 75 

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



<® « Kohlarten,' s. 22. 73 t Gardener's Chron. and Agricult. 



7° Godron, ' De l'Espece,' torn. ii. p. Gazette,' 1856, p. 729. 



52 ; Metzger, « Kohlarten,' s. 22. • n t Gardener's Chron. and Agricult. 



7 1 < Geograph. Bot.,' p. 840. Gazette,' 1855, p. 730. 



72 Godron, 'De l'Espece,' torn. ii. p. 75 Metzger, ' Kohlarten,' s. 51. 

 54 ; Metzger, ' Kohlarten,' s. 10. 



