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 nups. At the commencement of its 
erowth, the ascending axis is itself a bud. 
166. Buns are of two kinds, namely, the leaf-bud, containing 
the rudiments of a leafy branch, and the /lower-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, 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.) 
168. These scaly envelopes of the bud appear to be the rudimentary 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. . ; 
a. It is an interesting illustration of designing Wisdom, that buds are furnished 
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 
foliage immediately after their formation, without clothing them im 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 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 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 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 the 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. 
