22 



GENERAL BOTANY 



clusters of vigorous buds, as in the pine. In the elm the sub- 

 terminal bud of each cluster early replaces the true terminal bud 

 and continues the growth of the main axis of the branch or, in 

 the young tree, of the central trunk. Two or three vigorous buds 



below the subterminal 

 one form vigorous lateral 

 branches corresponding 

 to the false whorls of 

 the pine. These vigorous 

 lateral branches consti- 

 tuting a false whorl in 

 the elm are not, how- 

 ever, so numerous as in 

 the pine and are sepa- 

 rated by longer inter- 

 nodes (Figs. 11 and 12). 

 In the elm and other sim- 

 ilar trees some of the buds 

 on the terminal twigs 

 of the season below the 

 terminal cluster of vigor- 

 ous buds usually form 

 small dwarfed twigs, 

 while others remain la- 

 tent. These smaller lat- 

 eral twigs are ultimately 

 self -pruned, owing to the 

 fact that they are shaded 

 by their more vigorous 

 competitors, so that the mature portions of the trunk and branches 

 ultimately present a condition similar to that which exists in the 

 pines, with alternating false whorls of lateral branches and naked 

 segments of the central axis. The false whorls in the elm are 

 represented, however, by not more than two or three successful 

 branches in a whorl, instead of by many as in the pine. 



Often, as the elm grows older, a single vigorous branch grows, 

 each season, just below the bud which continues the main axis, 



FIG. 12. A mature elm tree illustrating the 

 spreading habit 



The numbers on the main trunk and branches are 

 similar to those in Fig. 11 



