ROOTS 



63 



largest at the top and gradually taper downward to a point, as 

 in the carrot, the napiform or turnip-shaped, which are large at 

 the top but do not taper, as in the turnip, and the fusiform or 

 spindle-shaped, which are largest in the middle and taper in both 

 directions, as in some radishes. Some fleshy roots, such as the 

 sweet potato (Fig. 37) and dahlia, are produced in bunches 

 or fascicles. 



The stored food materials are for use at some future date, 

 usually for the formation of flowers and fruits but sometimes for 



FIG. 40. Cross-section of stem showing dodder attached by haustoria or parasitic root. 



the direct production of new plants. In the radish the flowering 

 stalk is produced the same season that the root is produced ; but 

 turnips are usually kept over for a year and produce their 

 flowering stalks the second season. The sweet potato and dahlia 

 roots produce new plants directly. This storage of foods in the 

 roots corresponds to the storage of foods in the stems and leaves 

 (see page 74). The value of roots as food for man and other 

 animals depends on the character and amount of stored food, 

 upon the small amount of fibrous tissue and the absence of in- 

 jurious substances. Reproduction is a function of the roots in 

 the case of such plants as the sweet potato and the poplars to 

 which we have already referred. However, the production of 



