66 



A TEXT- BOOK OF BOTANY 



branches. In the tuber called Jerusalem artichoke, which is 

 developed by the subterranean stems of a kind of sunflower, 

 the nodes of the stem and the buds of branches are more 

 conspicuous than in the potato. Fleshy roots, such as those 

 of the sweet potato, should not be confused with tubers. 



(6) Bulbs. In some plants the main stem is very short 

 and is covered by numerous thickened, overlapping leaves 

 or leaf bases (usually called scales), the whole structure 



being a bulb. Bulbs 

 such as those of the 

 lily, hyacinth, tulip, and 

 onion are very familiar. 

 In this case the food 

 storage is chiefly in the 

 scales. Scaly bulbs are 

 those in which the scales 

 overlap, but are not 

 broad enough to enwrap 

 those within, as the lily 

 bulb (Fig. 65); coated 

 bulbs are those in which 

 the broad scales com- 

 pletely enwrap those 

 within, as the bulbs 

 of onions and tulips. 



Small bulbs, called bulblets, are borne by some plants on 

 parts above ground; as, for example, the bulblets that ap- 

 pear in the axils of the leaves of the tiger-lily and those that 

 replace flower-buds in the common onion. These bulblets, 

 when planted, have the power of producing new plants, as 

 do the subterranean bulbs. 



The above subterranean shoots, with their storage of 

 reserve food, enable plants to put out their aerial parts with 

 remarkable promptness and develop them with great 

 rapidity. As an illustration of a situation in which this 



FIG. 65. Scaly bulb of white lily: A, exte- 

 rior view; B, longitudinal section, showing 

 short stem and overlapping scales. After 

 BAILLON 



