THE SHOOT. 



19 



shoots which replace leaves in function and resemble them 

 in form. These branches may be either broad and flattened, 

 as in the "smilax " of the greenhouses, or they may be slen- 

 der and needle-like, as in the common garden asparagus 

 (fig. 67). In any case, since they replace leaves in function, 



Fig. 66. Fig. 67. 



Fig. 66. — Flower of Sedum acre, j, sepal; /, petal; st^ stamen; c, carpel. Magni- 

 fied 3 diam.- -After Baillon, 



Fig. 67. — Piece of a twig of asparagus; in the axil of the scale leaf, h, arise a fiower 

 shoot, and three leafless needle-like branchlets. Magnified about 2 diam.— After 

 Frank. 



they are abundantly supplied with green coloring matter for 

 manufacturing food. 



97. (d) Bulblets. — Other branches remain undeveloped 

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

 bulblets are easily detached and serve for propagation. (See 

 T[ 299.) They are to be found in many plants. In the 

 tiger-lily they occupy the axils of the leaves (fig. 180), and 

 are modified lateral buds, wliile in the garden onion they 

 usually replace the flowers. 



98. (e) 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. 68). 



