VEGETABLES 369 



it enables plants to start early and to develop rapidly. Of 

 course it must be tilled thoroughly and kept so. The plants 

 are also stimulated to rapid and vigorous growth by the free 

 use of suitable fertilizers, the best one being stable manure. 

 Where intensive gardening is practised, many vegetables are 

 started under glass and transplanted as soon as the weather 

 permits (as cabbage, early celery, sweet potatoes, tomatoes, 

 early lettuce), thus securing a much earlier crop. 



78. Classification of vegetables. It would be impossible 

 and unprofitable to enumerate the very numerous vegetables 

 in use. Some of the most common ones must be selected as 

 representatives. Any one who knows how to cultivate these 

 representative forms can extend the same principles to the 

 cultivation of any vegetable. 



Instead of classifying vegetables by the plant families to 

 which they belong, it will be more useful to classify them by the 

 plant structures they represent. This is more useful because 

 it is the structures that determine the methods of cultivation 

 and not the families. The six structures referred to above 

 will be used: (1) tubers, represented by the potato; (2) roots, 

 represented by the radish, turnip, parsnip, carrot, beet, and 

 sweet potato ; (3) bulbs, represented by the onion ; (4) leaves, 

 represented by cabbage, lettuce, and celery; (5) fruits, 

 represented by the tomato, cucumber, pumpkin, squash, and 

 melons; (6) seeds, represented by peas, beans, and sweet 

 corn. Of course this list probably does not include all of 

 the vegetables cultivated in any locality, but it includes the 

 principal ones. 



Tubers 



79. Potato. This is the most widely cultivated and 

 valuable of the tubers used as vegetables. The potato tuber 

 is a thickened branch of an underground stem (Fig. 45), and 

 it shows its stem character by its " eyes," which are buds in 

 the axils of minute leaves (scales). America is the native 



