70 THE STEM. 



ducing stems which, above the ground, are of annual duration 

 only, and do not become woody. Ex. the grasses, mullein. 



165. The most distinctive property of the stem is the forma- 

 tion and development of buds. At the commencement of its 

 gi-owth, the ascending axis is itself a bud. 



166. Buds are of two kinds, namely, the leaf-hud, containing 

 the mdiments of a leafy branch, and the flower-hud, containing 

 the same elements transformed into the organs of a flower, for 

 the purposes of reproduction. 



167. The leaf-bud consists of a minute, tender, growing point 

 of cellular tissue, originating with the pith, smTounded and pro- 

 tected by a covering of imbricated scales and incipient leaves. 

 (Fig. 22; 1.) 



168. These scaly envelopes of the bud appear to be the rudimentaiy leaves of 

 the precedmg year, foiined late in the season, arrested in their development by 

 the frosts and scanty nuti'iment, and reduced to a sear and hai'dened state. If 

 the bud of the maple or horse-chestnut (^sculus) be examined, when swollen in 

 spring, the student will notice a gradual transition from the outer scales to the 

 evident Uaves within. 



a. It is an interesting illustration of designing Wisdom, that buds are fimaislied 

 with scales only in wintry climates. In the torrid zone, or in hot-houses, where 

 the temperature is equalized through the year, plants develope their buds into 

 fohage immediately after their formation, without clothing them in scales. In 

 annual plants, also, the buds are destitute of scales, not being destined to sm-vive 

 the winter. Hence it is evident that the transformation of autumnal leaves into 

 scales, is a means ordained by the great Author of nature, to protect the young 

 shoots, in their incipient stages, from cold and moisture, — an office which they 

 effectually fulfil by their numerous downy folds, and theii* insoluble coat of 

 resin. * 



169. The original bud (plumule) of the embryo is at first 

 developed into a simple stem, and being itself continually repro- 

 duced, is always borne at the termination of that stem ; that is, 

 the axis is always termiiiated hy a hud. 



a. Besides this, the axis produces a bud (21, a) in the axil of each leaf, that is, 

 at the point just above the origin of the leaf-stalk. If these axillary buds remain 

 inactive, the stem will still be simple, as in the mullein. In general, however, 



*In many trees the scales of the buds are clorhed with a thick down. In others, as in the 

 horse-chestnut, balm of Gilead, and other species of poplar, the buds are covered with a 

 viscid and aromatic resin, resembling a coat of varnish. A considerable quantity may be 

 separated from a handful of such buds in boiling water. 



