314 BOTANY OF CROP PLANTS 



almost cylindrical, and narrow abruptly at both ends. The 

 roots are comparatively small (Golden Tankard). 



3. Oval or ^^ Intermediate.'^ — The roots in these are oval, 

 and intermediate in shape between globe and long varieties. 

 They vary in color (Giant Intermediate). 



4. Long. — Roots of this type are several times longer than 

 broad and project above the soil for a considerable propor- 

 tion of their length. They are heavy yielders. Both red 

 and yellow-skinned varieties (Long Red, Long Yellow) occur. 

 The ox-horn varieties have long twisted and horn-Hke roots. 



Composition and Uses. — I'he mangels vary in sugar con- 

 tent from 3 to 8 per cent., the Golden Tankard and Globes 

 having the highest percentage. Long varieties are relatively 

 low in sugar content but produce a greater tonnage per acre. 

 The water content varies from 85 to 92 per cent. Mangels 

 are being extensively grown for stock food. They are 

 one of the most important root crops. The root crops 

 include all plants whose underground vegetative parts, such 

 as rootstocks or roots, are utiHzed. Bulbs and tubers, 

 however, are usually excluded. Examples of root crops are 

 beets, mangels, turnips, carrots, rutabagas, sweet potatoes, 

 and artichokes. Root crops are used for human food and 

 also for forage. It must be kept in mind that all "root 

 crops" are not wholly roots, morphologically, but that in 

 some, such as the carrot, turnip, rutabaga, mangel and beet, 

 the lower two-thirds or more of the underground part is 

 root, the remainder stem ("crown"). Practically all 

 root crops are best adapted to localities with a cool growing 

 season. 



References 



GoFF, E. S.: Vegetables: Garden Beet. 6th Ann. Kept. N. Y. Agr. Exp. 



Sta., 120-132, 1887. 

 Kinney, L. F.: Spinach. R. I. Agr. Exp. Sta. Bull. 41: 99-131, 1896. 



