CHAPTER II. THE STEM. Q 



it is leaf-bearing, but in having its branches, for the most part, 

 arranged with mathematical regularity, and in the fact that the 

 growing-point is strictly apical instead of sub-apical. A stem 

 also increases in length by the growth of a terminal bud, and its 

 branches commonly originate from buds which spring from the 

 angle where the leaf joins the stem. We should first understand 

 the nature of buds. 



Buds are in reality rudimentary stems, with rudimentary 

 leaves compactly arranged upon them. In the growing season 

 we observe them constantly unfolding. The short bud-axis 

 which bears the minute closely packed leaf-rudiments is con- 

 stantly lengthening below, carrying the rapidly expanding leaves 

 farther apart and developing into a leafy branch, while above, 

 the bud is continually being renewed. Such a bud is not covered 

 with scales. Its leaves are all destined to develop into foliage. 



On some trees the buds that exist during the season of rest 

 are similar, except as respects the stoppage of their growth, to 

 those of the growing season. Such buds are usually of very 

 small size, and in some cases they are wholly or partially con- 

 cealed beneath the corky layer of the bark. Buds of this kind 

 are called naked buds. 



But most of our northern trees, at the approach of the cold 

 season, form scaly buds, which differ from those of the growing 

 season by having the outer leaf-rudiments transformed into scales 

 which never develop into true leaves, but whose sole function is 

 to protect those within, which in the spring are destined to 

 develop either into foliage or into floral organs. Such buds are 

 usually conspicuous, and they often attain a considerable size, 

 as, for example, in the Hickory. 



The scales of scaly buds are admirably adapted for protec- 

 tive purposes. They contain but little water, and are therefore 

 bad conductors of heat, thus preventing the occurrence of too 

 sudden changes of temperature in the interior of the bud, and 

 in many instances they have either a lining of downy hairs or 

 are covered with an insoluble varnish, which further increases 

 their non-conductivity at the same time that it prevents the 

 penetration of water. If the water were permitted ingress, by 

 freezing and thawing, it would injure, if not destroy, the delicate 

 organs which the scales enclose. 



