THE STEM. 



35 



Fig. 29. 



Some trees grow year after year from the terminal bud, winch closes up 

 into a winter-bud in autumn (fig. 30). In the Elm &c. the terminal 

 bud is not developed in the autumn, and the axillary bud next below 

 continues the growth. In the Horse-chestnut the terminal bud of the 

 annual shoot resolves itself into an inflorescence, and the growth of 

 the next year depends upon the axillary buds ; the same is the case in the 

 Lilac (Syringa vulgaris) (fig. 29), in which, 

 however, in this country, the terminal bud is 

 generally abortive or suppressed, and the pair 

 of axillary buds next below produce blos- 

 som, causing still more marked bifurcation 

 of the branches. 



As a general rule, of course, the frequent 

 suppression or conversion into blossom of 

 terminal buds tends to produce a bushy 

 mode of growth, and rice versa. In addition 

 to this, the relative force of development of 

 terminal and axillary buds is very important 

 in determining general form, as we see in 

 comparing the Black Poplar with its common 

 tall variety the Lombardy Poplar, or Coni- 

 ferous trees generally with deciduous trees. 

 Even among the individuals of the same 

 species we observe great differences in this Fl >; 29 - f h ot , f 



, , j. .. stroyed down to the first pair 



respect, dependent on external conditions; of axillary buds. 



for both Dicotyledonous trees and Conifers F'g- A shoot, with a terminal 



differ much in the relative proportion of main 



trunk and branches, when grown in close 



plantations, or standing in open situations. 



Ordinarily, only one bud exists in an axil 

 (fig. 30, 6); but frequent exceptions to this 

 occur, as in some species of Maple, in Honey- 

 suckles (tig. 31), and in the Walnut. How- 

 ever, one of these is generally much larger 

 than the rest, and is called the principal bud, 

 while the others are accessory. 



In some plants, as in many Solanaceae, the buds occur in an irregular 

 position, arising from the stem at a little distance above the leaf-axils. 

 This is supposed to be due to the adhesion of the bud with the stem, 

 and its uplifting with the latter as it lengthens. 



The Trunk of arborescent plants arises as an herbaceous stem 

 from the seedling, but usually becomes more or less woody before 

 the close of the first season ; in the autumn it ceases to develop in- 

 ternocles at its point, and the terminal bud closes up into a resting 

 winter-bud enclosed in leaf-scales ; buds of the same sort are pro- 

 duced in the axils of the leaves ; and all or part of them open in 

 the following spring, to produce a second generation of axes in the 

 form of shoots ; the same process being indefinitely repeated, a 

 branched trunk is produced. If the central stem is not much 



D 2 



and solitary 

 (6, 6, 6). 



Fig. 81. 



Numerous axillary buds of 

 Lonicera. 



