106 



THE STEM. 



by their bearing imperfect leaves themselves. In the Sloe, Pear, 



&c., many of the feebler 

 branches become spinose 

 or spinescent at the apex, 

 tapering off gradually in- 

 to a rigid leafless point. 

 These are less liable to 

 appear on the cultivated 

 tree, when duly cared 

 for, such branches being 

 thrown into more vigorous 

 growth. In the Hawthorn, 

 the spines spring from this 

 peculiar growth of the main 

 axillary bud, but it bears 

 an accessory bud (153) on 

 each side, one or the other 

 of which grows into an 

 ordinary branch. In the 

 Honey Locust, it is the 

 uppermost of several ac- 

 cessory buds, placed far 

 above the axil, that de- 

 velopes into the thorn 

 (Fig. 135). In this tree 



the spine itself branches, and sometimes becomes extremely com- 

 pound. Sometimes the stipules of the leaves develope into spines, 

 as in the Prickly Ash. 



173. The Subterranean Modifications of the Stem are scarcely less 



numerous and diverse than the aerial ; but they may all be reduced 

 to a few principal types. They are perfectly distinguishable from 

 roots by producing regular buds, or by being marked with scars, 

 which indicate the former insertion of leaves, or furnished with 

 scales, which are the rudiments or vestiges of leaves. All the 

 scaly roots of the older botanists are therefore forms of the stem or 

 branches, with which they accord in every essential respect ; they 



FIG. 135. Branching thorn of the Honey Locust (Gleditschia), an indurated branch devel- 

 oped from an accessory bud produced above the axil, a, Three buds under the base of the leaf- 

 stalk, brought to view in a section of the stem and leaf-stalk below. 



FIG. 136. Thorn of the Cockspur Thorn, developed from the central of three axillary buds ; 

 one of the lateral ones is seen at its base. 



