138 



A TEXTBOOK OF BOTANY 



[Ch. IV, 4 



ing deeply buried under the hark, and yet finally give origin 

 to branches. 



Where the terminal bud is notably prominent, as in Horse 

 Chestnut (Fig. 75), the axillary buds are largest just below 

 it, and progressively smaller farther back. Such a terminal 

 bud unfolds its flowers, stem, and foHage very quickly and 

 makes no more growth in length that season, though the upper 

 axillary buds may develop into branches. Such is definite 

 ANNUAL GROWTH. Where the terminal bud is relativelj^ small, 

 as in Elm, it continues to grow and jjroduce new leaves and 

 axillarjr buds all summer, and new branching takes place from 

 the lower new buds. Such is indefinite annual growth. 



The occurrence of a Ijutl in tlie axil of every leaf gives the 

 plant a great surplus, of which few ever develop into branches, 

 though all are capal)le of so doing. Generally speaking, 

 those nearer the outer ends (if the branches, and therefore 



nearest the light 

 and free space, 

 a r e the ones 

 which develop, 

 though if the ter- 

 minal, or outer 

 axillary, buds be- 

 come destroyed, 

 whether by frost, 

 insect ravage, or 

 experimental de- 

 sign, the next 

 lower develoj) in 

 their places. 

 Since all are 

 capable of de- 

 velopment, it is evident that some factor controls them 

 collectively, either inhiljiting the development of some or 

 stimulating that of others, — a subject to which we shall 

 later return under Growth. 



Fig. 92. — A bud, of unusuallj- elongated form, 

 of a water weed, Elodta caiiaden^U, in exterior \iew 

 and section, showing the develoijnicnt of le;nes ; 

 X 1-50. (After L. Kny.) 



