LESSOK 4.] GROWTH OF PLANTS FROM BUDS. 25 



appears at all ; in its place the uppermost pair of axillary buds grow, 

 and so each stem branches every year into two ; making a re- 

 peatedly two-forked ramification. 



53. In these and many similar trees and shrubs, most of the shoots 

 make a definite annual growth. That is, each shoot of the season 

 develops rapidly from a strong bud in spring, — a bud which gen- 

 erally contains, already formed in miniature, all or a great part of the 

 leaves and joints of stem it is to produce, — makes its whole growth 

 in length in the course of a few weeks, or sometimes even in a few 

 days, and then forms and ripens its buds for the next year's similar 

 rapid growth. 



54. On the other hand, the Locust, Honey-Locust, Sumac, and, 

 among smaller plants, the Eose and Raspberry, make an indefinite 

 annual growth. That is, their stems grow on all summer long, 

 until stopped by the frosts of autumn or some other cause ; con- 

 sequently they form and ripen no terminal bud protected by scales, 

 and the upper axillary buds are produced so late in the season 

 that they have no time to mature, nor has the wood time to solidify 

 and ripen. Such stems therefore commonly die at the top in winter, 

 or at least all their upper buds are small and feeble ; and the growth 

 of the succeeding year takes place mainly from the lower axillary 

 buds, which are more mature. Most of our perennial herbs grow 

 in this way, their stems dying down to the ground every year : the 

 part beneath, however, is charged with vigorous buds, well pro- 

 tected by the kindly covering of earth, ready for the next year's 

 vegetation. 



55. In these last-mentioned cases there is, of course, no single 

 main stem, continued year after year in a direct line, but the trunk 

 is soon lost in the branches ; and when they grow into trees, these 

 commonly have rounded or spreading tops. Of such trees with 

 deliquescent stems, — that is, with the trunk dissolved, as it were, 

 into the successively divided branches, the common American Elm 

 (Fig. 54) furnishes a good illustration. 



66. On the other hand, the main stem of Pines and Spruces, as 

 it begins in the seedling, unless destroyed by some injury, is carried 

 on in a direct line throughout the whole growth of the tree, by the 

 development year after year of a terminal bud : this forms a single, 

 uninterrupted shaft, — an excurrent trunk, which can never be con- 

 founded with the branches that proceed from it. Of such spiry or 

 ipire-shaped trees, the Firs or Spruces are the most perfect and 

 3 



