70 THE STEM. 



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

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



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

 tion and development of buds. At the commencement of its 

 growth, the ascending axis is itself a bud. 



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

 the rudiments of a leafy branch, and the fiower-bud, 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, groiving point 

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

 tected by a covering of imbricated scales and incipient leaves. 

 (Fig. 22; 1.) 



168. These scaly envelopes of the bud appear to he the i-udimentar}- leaves of 

 the preceding year, formed late in the season, arrested in their development by 

 the frosts and scanty nutriment, and reduced to a sear and hardened 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 leaves within. 



o. It is an interesting illustration of designing Wisdom, that buds are furaished 

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

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

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

 annual plants, also, the buds are destitute of scales, not being destined to survive 

 tlie 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 tlie young- 

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

 effectually fulfil by their numerous downy folds, and their 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 terminated by 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 soales of the buds are clothed with a tliick down. In others, as in the 

 horsL'-chestiiut, balm of Gilcad, and olhcr species of poplar, the buds are covered with a 

 viscid and aromatic resin, reseml)liiig a coat of varnish. A considerable quantity may be 

 separated from a handful of such buds in boiling water. 



