THE PLANT-BODY 



21 



branching is concealed. On the other hand, two lateral branches 

 may develop close to the growing-point, as in Cerastium and other 

 Caryophyllacese, and a false dichotomy results. 



Monopodial Branching Monopodial branching consists in the for- 

 mation of secondary lateral branches, while the original growing- 

 point remains undivided. This is by far the commonest type of 

 branching, especially among the higher plants (Fig. 11, A). 



Adventitious Branching. Branches are not infrequently formed 

 on the older part of a plant, which are quite independent of the 

 growing-point. Such shoots, or " suckers," as arise from the roots 

 of the Ailanthus, or Locust, or the leafy shoots developed from the 

 leaves of Bryophyllum and the tip of the leaf in the Walking Fern 

 (Fig. 11, C), are entirely secondary in their origin. Such branches 

 are known as " Adventitious " shoots, to distinguish them from the 

 normal branches. Such adventitious shoots must be carefully dis- 

 tinguished from the apparently secondary shoots which arise from 

 the older parts of plants where they have remained dormant. 

 Thus, in some species of Horsetails (Equisetum), lateral buds are 

 regularly formed near the growing-point, but ordinarily remain unde- 

 veloped. Under certain conditions, however, they may be made to 

 develop. 



Origin of Branches Branches usually develop as outgrowths of 

 the superficial tissues ; and such branches are said to be exogenous. 

 More rarely the fundament of the branch is formed within the 

 body and breaks through the overlying tissue. Such endogenous 

 branching is the rule in the formation of roots in vascular plants, 

 but is rare in other cases. In some Liverworts the adventitious 

 branches are of endogenous origin. 



Symmetry 



Plants generally exhibit marked 

 arrangement of the 

 tissues and the po- 

 sition of the organs 

 with reference to 

 each other. This 

 symmetry may be 

 either Radial or 

 Bilateral. Radially 

 symmetrical parts 

 are those which 



may be equally 

 -,..-,-,, J FIG. 12. Radial 



divided by more perfoliatum . B , 



than two vertical telmateia ( x 3) . 



symmetry, both as regards the 



symmetry. A, flower of Hypericum 

 cross-section of internode of Equisetum 



