MORPHOLOGY OF STEMS. 



liable to appear on the cultivated tree, when duly cared for, such 

 branches being thrown mostly into more vigorous growth. In 



the Hawthorn, the spines 

 spring from the main axillary 

 bud. while accessory buds 

 (76), one on each side, ap- 

 pear, and grow the next sea- 

 son into ordinary branches. 

 In the Honey-Locust, it is 

 the uppermost of several ac- 

 cessoiy buds, placed Car above 

 the axil, that develops into 

 the thorn (Fig. 00) . Here the 

 spine itself usually branches, 

 and sometimes becomes ex- 

 tremely compound. 



11:5. For spines which are 

 homologous with leaves, or 

 parts of a leaf, see Sect. IV. 

 227. Prickles, such as those 

 of Brambles and Roses, are 

 superficial outgrowths from 

 the bark, of a different nature 

 (:>*.'!). and of small morpho- 



97f' 



114. Subterranean Stems are hardly less diverse than the 

 aerial. The}- are classed as RHIZOMES, TUBEUS, COUMS, and 

 BULBS, the forms passing one into another by gradations. 



11;"). Rhi/oma (Hliizome, or in English ROOTSTOCK) is a gen- 

 eral name for any horizonal or oblique perennial stem, which lies 

 on the ground or is buried beneath its surface. It sends off 

 roots of a fibrous or slender sort wherever it rests on or is cov- 

 ered by llic soil, and usually produces from its apex some kind 

 of aerial stem, cither lealy or as a flower-stalk (*><//. ;i~). 

 which rises into the air and light. Before morphology was 

 understood, rootstocks were called creeping roots, srnfi/ roots, A:c. 

 Some are slender, such as those of Mints (Fig. 99), of most 

 Sedges (Fig. !i*l. and of Couch-( Irass. Their canline nature is 

 evident, from their structure and appearance : their nodes and 

 internodes are well marked, the former 1 tearing leaves reduced to 



FIG. %. Branc'hini; thorn of the Honey-Locust (Gleditschia). an indurated braiieb 

 developed from an accessory bud produced above the axil. a. Three buds under the 

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



FIG. 9". Thorn of the' Cnekspur Thorn, developed from the central of three axillary 

 buds ; one of the lateral buds is seen at its base. 



