20 



BOTANY 



PART 1 



unequally ; the weaker becomes pushed to one side and ultimately 

 appears as a lateral branch (Fig. 19). Although a relationship as 

 regards position is generally apparent between the origin of leaves and 

 the lateral shoots, in the system of branching resulting from such a 

 liifurcation of the vegetative cone this connection does not exist. 

 In the more highly developed Bryophytes, particularly in the true 

 ]\Iosses, new shoots arise obliquely below the still rudimentary leaves 

 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 of the bud. 

 Shoots thus produced in the axils 

 of leaves are termed AXILLARY 

 SHOOTS. The leaf, in the axil of 

 Avhich a shoot develops, is called 



Fio. 18. — Longiturlinal section of a bifurcat- 

 ing shoot (j)) of Lycopodium alpinum, 

 showing equal development of the rudi- 

 mentary shoots, p', p" ; h, leaf rudiments ; 

 c, cortex ; /, vascular strands. (After 

 Heoelmaier, X 60.) 



Fig. 19. — Bifurcating shoot (j') of LycojwdUnn 

 inundatum, showing unequal development 

 of the rudimentary shoots, p', p" ; h, leaf 

 rudiments. (After Heoelmaier, x 40.) 



its SUBTENDING LEAF. An axillary shoot is usually situated in a line 

 A\-ith 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 Lorncera, Gkditschia, Gymnodadus, or side 

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

 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. 



