20 BOTANY PART i 



at some distance from the growing point. In the Phanerogams new 

 shoots generally arise in the axils of the leaves. In the accom- 

 panying illustration of a longitudinal section of a phanerogamic 

 shoot (Fig. 17) the rudiment of a shoot (g) is just appearing in 

 the axil of the third uppermost leaf ; in the axils of the next older 

 leaves the conical protuberances of the embryonic leaves are 

 already beginning to appear on the still rudimentary shoot. Shoots 

 thus produced in the axils of leaves are termed AXILLARY SHOOTS. 

 The leaf, in the axil of which a shoot develops, is called its SUH- 

 TENDING LEAF. An axillary shoot is usually situated in a line 

 with the middle of its subtending leaf, although it sometimes 

 becomes pushed to one side. As a rule, only one shoot develops 

 in the axil of a leaf, yet there are instances where it is followed 

 by additional or ACCESSORY SHOOTS, which either stand over one 

 another (serial buds), as in Lonicera, Gleditschia, Gymnoclcuhis, or side 

 by side (collateral buds), as in many Liliaceae, e.g. species of AUnnn 

 and Muscari. 



Although in the vegetative regions, i.e. the regions in which 

 merely vegetative organs are produced, the rudiments of the new 

 shoots of phanerogamic plants make their appearance much later 

 than those of the leaves, in the generative or flower-producing regions 

 the formation of the shoots follows directly upon that of their sub- 

 tending leaves, or the shoots may even precede the leaves. In this 

 last case the subtending leaves are usually either poorly developed 

 or completely suppressed, as in the inflorescence of the Cruciferae. 



The bud forming the end of a shoot is called the terminal bud, 

 while those borne on the sides of the shoot are the lateral buds. 



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 adventitious shoots frequently spring from old 

 stems, also from the roots of herbaceous plants (Brassica oleracea. 

 Anemone sylvestris, Convolvulus arrensis, Eumex Acetosella), or of bushes 

 (J,'n!iiis, Rosa, Corylus), or of trees (Populus, Ulmus, Rolinia). The)' 

 may even develop from leaves, as in Cardamim 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. 



Leaves and also normal shoots, which make their appearance as out- 

 growths from the portions of the parent shoot, still in an embryonic 

 condition, have an external or EXOGENOUS origin. Adventitious 

 shoots, on the other hand, which arise from the older parts of stems 

 or roots, are almost always ENDOGENOUS. They must penetrate the 

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



