MORPHOLOGY OF HIGHER PLANTS. 



321 



appearing as little protuberances, sometimes spoken of as pri- 

 mordia, on the stem. Their origin differs from that of the root 

 branches, in that they arise from meristematic or embryonic tissue 

 developed just beneath the epidermis. The branches, like the 

 main axis, manifest negative geotropism, although to a lesser 

 degree. They likewise possess a growing point at the apex, 

 covered with embryonic leaves (Fig. 179). Not infrequently 

 more than one branch arises in the leaf axil. 



Buds may be defined as undeveloped shoots in which the 

 foliage is yet rudimentary. The buds at the ends of stems or 



Fig. 179. A, longitudinal section through the apical region of the stem of the embryo 

 of a bean (Phaseolus fnultiflorus) \ ss, apex; pb, parts of the two first leaves, and their 

 axillary buds (k, k,); r, periblem or primary cortex. B, diagram of longitudinal section 

 through winter bud of Qit-ercus coccinea: P, growing point; L, young leaves; SB, stem 

 branches; F, fibro Vascular bundle. — A, after Sachs. 



branches are known as apical, or terminal buds, and those situ- 

 ated in the axils of the leaves, as axillary buds. In some cases 

 they are protected by scales, as in hickory, when they are known as 

 scaly buds ; while buds which are not thus protected are called 

 naked buds. They are further distinguished as leaf, flower, and 

 mixed buds, as they develop into leaves or flowers, or both. 



We have to distinguish between overground shoots and under- 

 ground shoots. The former are sometimes designated as epi- 

 geous (upon the earth) and the latter as hypogeous (under the 

 earth). 



