Ch. IV, 4] 



DEVELOPMENT OF STEMS 



137 



center shows very clearly the characteristic tapering stem, 

 with the series of leaves in all stages of development 

 (Fig. 90). 



Within the buds the leaves are arranged in various ways, 

 either overlapping, or each folded by itself on its midrib, or 

 inrolled from margins or tip. The arrange- 

 ments are called collectively vernation, and 

 have importance in descriptive taxonomy. 



The most prominent, and commonly the 

 largest, buds are those which are terminal 

 on the main stems and branches, and which 

 continue the stem growth. More abundant 

 are the axillary buds which develop in the 

 upper angle between leaf and stem, and are 

 nearly as numerous as the leaves themselves, 

 at least in exogenous plants. The functional 

 reason for the usual occurrence of buds in this 

 position is found, no doubt, partly in the near- 

 ness to the source of food indispensable for 

 their development, and partly in the favorable 

 structural opportunity to make connection 

 with the main stem in the gap left in the 

 fibro-vascular cylinder above the leaf base 

 (page 1 19) . In a few plants, of which Tatarean 

 Honeysuckle and Red Maple are examples 

 (Fig. 91), more than one bud occurs in each 

 axil, either side by side, or one above another, 

 the extra buds being called accessory. 

 Finally, while in many plants no buds other accessory buds ; 

 than terminal or axillary occur, in others they Gray.) 

 develop in almost any position, especially at 

 some place of injury; and these so-called adventitious 

 buds produce the branches in irregular positions, as often 

 seen in Willows and some other woody plants. Not all 

 irregular branching, however, results from adventitious 

 buds, for axillary buds often remain latent for years, becom- 



Fig. 91.— A 

 twig of Red 

 Maple, showing 



