n6 THE SCHOOL GARDEN BOOK 



fleshy tap-root. They are biennials in their origin, storing 

 up food the first year underground and using this the second 

 year when flowering and producing seed, so they are hardy 

 enough to be sown early and harvested late or even after a 

 winter in the ground. While varieties of some have been 

 obtained which will produce edible roots within a few weeks, 

 most need a long season to reach maturity, and are still grown 

 as biennials to secure seed. 



The only important Tuber Crops are the potato and sweet 

 potato. Potato tubers differ from roots in that each is de- 

 veloped as a store of food at the end of a root-stock, each 

 thickened tuber having buds or eyes from which new branches 

 with leaves may develop. A sweet potato, like a dahlia, is 

 more a thickened root than a root- stock, for the eyes are on 

 the end toward the main plant stem, while the other end is 

 rooted. A potato has no roots on the tuber, and the eyes 

 are clustered on the free end, like any branch above ground. 



The most important Bulb Crops are the onions i chives, 

 garlic, and leek. In these bulbs the root-stock is greatly 

 modified into a series of scales, one lapping upon the other 

 in a way familiar to every one who ever saw the structure of 

 an onion. The true roots develop from the base of these 

 scales while the leaves are sent out from the upper ends. 

 These vegetables are grouped together more because they 

 belong to the same plant family rather than because alike 

 in culture. Chives, for example, are grown as perennials 

 for their leaves, which are used like herbs in seasoning, 

 and they are reproduced more by division of the clumps 

 than from seed. And in case of the leek, no large bulb is 

 formed, but the long, thick, blanched bases of the leaves 

 are used, being stored green like celery. 



