FLESHY ROOTS 127 



root. The ring of ink marks the boundary between the 

 cortex and the central axis. Cut through one of the sec- 

 tions vertically and notice that the portion marked " vascu- 

 lar cylinder " in the hard root has here been replaced by 

 a soft, nutritious substance. Put a drop of iodine on it 

 and see if it contains starch. Peel off a part of the cortex 

 and observe that the woody or conducting portion of the 

 interior is confined principally to a thin layer on the out- 

 side of the thickened fleshy axis. Can you tell now why 

 the course of the red ink in this kind of root is confined 

 mainly to a ring just inside the cortex, while in hard roots 

 in the newer, active parts of them at least it runs 

 through the whole of the central axis? (Sec. 174.) 



This band of woody or vascular tissue, as it is called, 

 becomes very evident in old turnips and radishes. In the 

 beet it is arranged peculiarly, being disposed in concentric 

 layers alternating with the fleshy substance, instead of 

 in a single layer next the cortex. These vascular rings 

 give to a section of beet the appearance of certain woody 

 stems with their rings of annual growth, but their origin 

 is quite different. 



180. Function of Fleshy Roots. What is the use of 

 fleshy roots ? We give a practical answer to this question 

 every time we eat a carrot or a turnip. Fleshy roots are 

 especially useful to biennials, a name given to herbs that 

 take two years to perfect their fruit, in contradistinction to 

 annuals, which complete their life history in a single season. 

 The biennials spend their first year in laying by a store of 

 nourishment which they use up the next year in producing 

 a crop of seed provided man does not forestall them 

 and appropriate it to his own use. This explains why a 

 radish or a turnip is so dry and tasteless the second year ; 

 nearly all of its store of food has been exhausted in matur- 

 ing seed. 



181. Perennial Herbs are those that live on indefinitely 

 from year to year. Many of these, like the dahlia and 

 hawkweed, die down above ground in winter but are en- 



