THE SHOOT. 93 



In form. These cladophylls may be either broad and flat- 

 tened, as in the "smilax" of the greenhouses, or they 

 may be slender and needle-like, as in the common garden 

 asparagus (fig. 105). In any case, since they replace leaves 

 in function, they are abundantly supplied with green color- 

 ing matter for manufacturing food. 



113. (</) Bulblets. — Other branches remain undeveloped 

 as buds, but their leaves become thick and fleshy. These 

 bulblets are easily detached and serve for propagation. (See 

 ^| 364.) They are to be found in many plants. In the 

 tiger-lily they occupy the axils of the leaves (fig. 294), 

 and are modified lateral buds, while in the garden onion 

 they usually replace the flowers. 



114. (c) Tubers. —Some underground shoots have their 

 ends suddenly and greatly enlarged, adapting them to the 

 storage of food. They are then called tubers. In the white 

 potato the tuber consists of several terminal internodes of 

 an elsewhere slender underground stem, the "eyes" being 

 lateral buds in the axils of minute scale leaves. In a few 

 plants tubers may even be formed above ground, as in certain 

 polygonums whose flowers are often replaced by little tubers 

 which are readily detached (fig. 106). 



115. (/) Tendrils.— Some shoots take the form of slender, 

 leafless, sensitive tendrils, which assist the plant in climbing 

 by coiling about suitable objects (fig. 107). 



116. (g) Thorns. — Many plants produce defensive shoots, 

 which are leafless, rigid, short, and sharp, called thorns, 

 which may be either simple or branched (fig. 108). The 

 honey-locust furnishes an excellent example of branched, or 

 compound, thorns. 



Leaves themselves may be developed as tendrils or as 

 thorns, so that it must not be assumed from appearance alone 

 that such members are forms of the shoot. Observation of 

 the origin and relation of the members will reveal their true 



