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 rudiments of a leafy branch, and the flower-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, groivmg point 

 of cellular tissue, originatmg 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 be the mdimentaiy leaves of 

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

 the frosts and scanty nntriraent, and reduced to a sear and hardened state. If 

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

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

 evident haves within. 



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

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

 the temperature is ec[ualized througli the year, plants develope their buds into 

 foliage immediately after their foi-mation, 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 ai;tumnal 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 ofiSce which they 

 effectually fulfil by their numei'ous do\vny folds, and their insoluble coat of 

 resin. * 



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

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

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

 the axis is alicays terminated by a bud. 



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 tlie scales of the buds are clothed 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. 



