122 



BOTANY 



PART I 



seems to spring directly from its subtending leaf ; or, finally, the subtending leaf 

 may become attached to its axillary shoot, and, growing out with it, may thus 

 appear to spring from it (Fig. 143). 



It is the rule in Phanerogams that normal shoots arise from the embryonic 

 tissue of the growing point of the parent shoot. When they are apparent at a 

 greater distance from the apex it can usually be shown that embryonic substance 

 has been reserved at the proper points for their formation. 



Shoots developing in predetermined positions on young parts 

 of the plant are designated NORMAL, in contrast to ADVENTITIOUS 

 SHOOTS, which are produced irregularly from the old or young portions 

 of a plant, such as stems, roots, or leaves, and usually arise from 

 permanent tissue which returns to the meristematic condition. 

 Adventitious shoots, which arise from the older parts of stems or 

 roots, are almost always ENDOGENOUS. They must penetrate the 



FIG. 144.^, ground plan or diagram, and B, lateral view of a lateral bud of a Monocotyledon 

 with a divergence of ; m, parent axis ; db, subtending leaf borne on this ; t, the daughter 

 axis ; vb, bracteole on this ; h, posterior, and v, anterior sides of the daughter shoot. 



outer portions of their parent shoot before becoming visible. Adven- 

 titious shoots formed on leaves, however, arise, .like normal shoots, 

 exogenously. 



Such adventitious shoots frequently spring from old stems, also from the roots 

 of herbaceous plants (Brassica oleracea, Anemone sylvestris, Convolvulus arvensis, 

 Rumex Acetosella], or of bushes (Rubus, Rosa, Corijlus), or of trees (Populus, 

 Ulmus, Robinia). They may even develop from leaves, as in Cardamine pratensis, 

 Nasturtium officinale, and a number of Ferns. An injury to a plant will frequently 

 induce the formation of adventitious shoots, and they frequently arise from the 

 cut surface of stumps of trees. Gardeners often make use of pieces of stems, 

 rhizomes, or even leaves as cuttings from which to produce new plants ( 6V ). When 

 the buds in this case do not arise from existing growing points but are new-formed 

 from permanent tissue, the process is spoken of as REGENERATION (of. the section 

 on Physiology). 



(b) The Position of the Leaves of Lateral Buds. When the 

 relations of position in a lateral branch of any order are to be 



