34 PRINCIPLES OF BREEDING. 



southern variety brought northward, gradually dwindles 

 in size and rijDens earlier until it reaches a type special- 

 ly fitted to its latitude. 



Variation, although the same in kind, is greater in 

 degree, among domesticated plants than among ani- 

 mals. From the single wild variety of the potato as 

 first discovered and taken to Europe, have sprung 

 innumerable sorts. Kemp, in his work on Agricultural 

 Physiology, tells us, that on the maratime cliffs of 

 England, there exists a little plant with a fusiform root, 

 smooth glaucous leaves, flowers similar to wild mus- 

 tard and of a saline taste. It is called by botanists, 

 Brassica oleracea. By cultivation there have been 

 obtained from this insignificant and apparently useless 

 plant — 



1st, all borecoles or kails, 12 varieties or more. 



2d, all cabbages having heart. 



3d, the various kinds of Savoy cabbages. 



4th, Brussels sprouts. 



5th, all the broccolis and cauliflowers which do not 

 heart. 



6th, the rape plant. 



Yth, the ruta baga or Swedish turnip. 



8th, 3^ellow and white turnips. 



9th, hybrid turnips. 



10th, kohl rabbi. 



