56 



MORPHOLOGY OF STEMS. 



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

 branches being thrown mostly into more vigorous growth. In 



the Hawthorn, the spines 

 spring from the main axillary 

 bud, while accessor 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- 

 cessor}- buds, placed far above 

 the axil, that develops into 

 the thorn (Fig. 96) . Here the 

 spine itself usually branches, 

 and sometimes becomes ex- 

 tremely compound. 



113. For spines which are 

 homologous with leaves, or 

 parts of a leaf, see Sect. IV. 

 227 a . Prickles, such as those 

 of Brambles and Roses, are 

 superficial outgrowths from 

 the bark, of a different nature 

 (383) , and of small morpho- 

 logical signification. 



114. Subterranean Stems are hardly less diverse than the 

 aerial. They are classed as RHIZOMES, TUBERS, CORMS, and 

 BULBS, the forms passing one into another b}- gradations. 



115. Rhizoma (Rhizome, 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 bj* the soil, and usualty produces from its apex some kind 

 of aerial stem, either leafy or as a flower-stalk (scape, 97), 

 which rises into the air and light. Before morphology was 

 understood, rootstocks were called creeping roots, scaly roots, &c. 

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

 Sedges (Fig. 98), and of Couch-Grass. Their cauline nature is 

 evident from their structure and appearance ; their nodes and 

 internodes are well marked, the former bearing leaves reduced to 



FIG. 96. Brandling thorn of the Honey-Locust fGleditschia). an indurated branch 

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

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



FIG. 97. Thorn of the Cockspur Thorn, developed from the central of three axillary 

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



