356 



GENERAL BOTANY 



FIG. 209. Accessory buds of box 

 elder (Negundo) 



A, front view ; B, two groups seen 

 in profile 



Buds. Buds may be classified 

 on the basis of their position on 

 the main axis and branches or 

 according to structure and devel- 

 opment. On the basis of position, 

 buds are terminal, lateral, axil- 

 lary, accessory, or -adventitious. 



The terms terminal and lateral 

 (or axillary) are self-explanatory, 

 since such buds are located at 

 the apex of a stem or branch or 

 in the axils of leaves. 



The term accessory, or super- 

 numerary, applies to cases in 

 which several buds arise in the 

 axil of a single leaf, as in maples 



(Fig. 209). Adventitious buds arise at points on the stem other 



than in the leaf axils and are usually 



the result of an injury. 



Buds are also classified on the basis 



of structure and development. Thus, 



branch or leaf buds develop into branches 



with leaves; flower buds form single 



flowers, or, more frequently, inflores- 

 cences, as in the common types of trees ; 



mixed buds give rise to both flowers and 



shoots with leaves, as in the apple and 



maple. 



Roots. The primary root is the first 



root of the embryo and seedling. In 



most dicotyledons the primary root 



forms a taproot or a single main root, 



with small lateral roots, as in the beet, 



carrot, and dandelion (Fig. 210). The 



primary root may be permanent or tem- 

 porary, being replaced in the latter instance by secondary roots 



which grow out from the lower part of the stem. 



FIG. 210. Fleshy taproot 

 of the carrot 



