EAI3ST ON THE ROOT CROPS. 157 



plant we eat consists of the succulent slioots which force 

 their way up through the sand in spring, and which we 

 intentionally lengthen out and blanch by the device of 

 artificial banking. Gardeners say that it flourishes best 

 even now when surrounded by its natural element sand 

 from the sea-shore. The origin of our radish is not known 

 with certainty, though it probably represents an improv- 

 ed southern variety of the jointed charlock that grows by 

 road-sides in many parts of England. 



All these are purely useful variations on the one primi- 

 tive theme ; but there are some other crucifers whose 

 flowers have been developed into a higher state of per- 

 fection by insect selection, and many of these supply us 

 with a groundwork for ornamental garden blossoms. 

 Simplest among them are the little white alyssum, with 

 its sweet honey perfume, and the queer one-sided candy- 

 tufts of old-fashioned gardens, whose two outer petals 

 have grown longer and broader than the two inner ones, 

 so as to present a larger total attractive surface, thus 

 clearly bearing witness on their very faces to the inter- 

 vention of insect agency. Even higher in this respect 

 are the stocks and gillyflowers, whose petals are raised 

 on long claws, so as to form a tube for the preservation 

 of the honey from minor flies and beetles. These and a 

 vast number of other garden plants or wild weeds are all 

 shown by their common points of structure to be de- 

 scended from a single original ancestor ; and the peculi- 

 arities which natural selection has stamped upon them 

 have in many cases been further developed or exagger- 

 ated by the action of man. In fact it would almost seem 

 as though we had but to set an ideal before our eyes, 

 and then by constant selection to bring it about bodily in 

 the sphere of concrete reality. On the other hand, 

 wherever the natural tendencies exist we may produce 



