70 . '^nv. .'.TCM. 



ducing stems which, above the ground, are uf 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 it.s 

 growth, the ascending axis is itself a bud. 



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

 the nidiments of a leafy branch, and the fiowcr-hud, containing 

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

 the purposes of reproduction.^ 



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

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

 tected by a covering of imbricated scales and incipient leaves^ 

 (Fig. 22; 1.) 



1 RS. Tlicse scaly envelopes of the bud appear to be the nidimentary leaves of 

 the precedinf^ year, formed late in the season, arrested in their development by 

 the frosts and scanty nutriment, and reduced to a sear and hardened siate. If 

 the bud of the maple or horse-chestnut (.^sculus) be examined, v/hen swollen in 

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

 evident haves within.' 



a. It is an interesting illustration of designing Yv^isdom, that buds arc fr.rnished 

 Avith scales only in wintry climates, j' In the toii-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 

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

 scales, is a means ordained by the great Author of natiu'e, to protect the young 

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

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

 resin.* 



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

 developed into a simx>lc stem, and being itself conlinually repro- 

 ditced, is always borne at the termination of thttt stem ; that is, 

 the axis is always terininaied hi/ 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 

 inacti^•e, the stem \\-ilI still be simple, as in the mullein. In general, howe\xr, 



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

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

 viscid and aromatic resni, resembling a coat of varnish. A coiisidfrablc quantity may be 

 separated from a handful of such buds in boiUng water. 



