12 VERTICAL SECTION OF BUD [CH. 



of new lateral buds in the angles between leaf and stem 

 the so-called leaf-axils and which would subsequently 

 have developed in their turn to buds with similar 

 structure. 



All these matters can be made clearer by cutting the 

 Lettuce, Cabbage, Lilac bud, &c. accurately down the 

 middle, so that the longitudinal section exactly halves 

 the stem and its young leaves. 



Such a longitudinal section shows still more clearly 

 that the bud consists of a conical prolongation of the 

 stem, from which, on all sides, the young leaves are given 

 off as lateral outgrowths, and this in such a way that the 

 youngest of the leaves arise at points nearer the true tip 

 of the stem than does any older one. One difference which 

 is soon obvious is that while in the Lettuce, Cabbage, &c. 

 the leaves are arranged in spirals, in the Lilac and others 

 they are opposite on the axis, as seen in Fig. 5. 



If the bud is sufficiently advanced, moreover, we can 

 see that the more developed leaves become successively 

 removed further and further apart from the younger ones 

 and are therefore no longer to be reckoned as con- 

 cerned in the bud proper by the elongation of the 

 internodes between them and the latter, the apex of the 

 stem in the bud being therefore carried higher up into 

 the air. At the same time these maturing leaves expand, 

 partly by the flattening out of the hitherto incurved and 

 concave upper surface, and partly by the enlargement 

 of the latter and the elongation of the petiole, during the 

 process of growth. 



A careful examination of sections of the plumule or first 

 bud of successively older germinating seeds will show the 

 student that it is composed in exactly the same way of 

 a series of overlapping young leaves, curved in over the 

 true apex of the primary shoot, and so developed on the 



