930 RAPHANUS. CCLASS XV. ORDER II. 



ft. oblonga. The root oblong, tapering. The common Garden 

 Radish, of which there are several varieties, white, pink, 

 red, &c. 



y. okifera. The root elongated, scarcely fleshy. The Oil- 

 seeded Radish. 

 2. NIGER. The root somewhat hard, fleshy, and of an acrid 



flavour. 

 . vulgaris. The root oblong, black externally, white within, 



Common Spanish Radish. 

 (3. rotundus. The root roundish, black externally, white 



within. Turnip Spanish Radish. 



y. grisens. The root grey externally. Grey Spanish Radish. 

 $. albus. The root globose, depressed, white. White Spanish 



Radish. 



Their use and mode of cultivation are too well known to require 

 description here. Some are grown for spring use, others for the 

 summer, autumn, and winter. 



The pink colour of the rind of the common Garden Radish, when 

 scraped or bruised in water, is changed to a dull purplish blue, and is 

 a delicate test of acids, which, upon being added to it, immediately 

 change it to its original beautiful pink colour ; from which it ap- 

 pears that the pink colour depends upon the presence of some acid in 

 the rind, which escapes upon exposure to the atmosphere. This acid 

 is, doubtless, the carbonic. We have before alluded to this property of 

 colour in plants, and endeavoured to point out some use to which it 

 may be applied in the cultivation of flowers by improving their 

 colours, &c., (see Papaver, p. 750). 



