CHAPTER XXVI 



SEED-BEARING PLANTS (Continued) 



GYMNOSPERMS 



LIFE HISTORY OF THE PINE 



Description of the Tree 



365. The Trunk. — Everyone is so familiar with the 

 general features of pine trees as to render a detailed de- 

 scription unnecessary here. The main stem or trunk is 

 normally a straight vertical shaft, that may be traced from 

 the ground to the apex of the tree (Fig. 304). Such a 

 trunk is called excurrent, in contrast to the opposite type 

 which may be traced for only a short distance from the 

 ground, to a point where it divides into the main 

 branches or limbs. The latter type of trunk is termed 

 deliquescent (Fig. 305). 



The excurrent trunk results from the fact that the 

 main stem, as well as the lateral branches, always has a 

 terminal hud, which carries the trunk upward from year 

 to year. Trees may continue to increase in height each 

 season, until they have reached the limit for the given 

 species. Many factors may, of course, modify the height, 

 among which is the limit of height to which the species 

 can raise sap. Some species of pine attain a height of 

 160 feet. 



366. Branching. — At first glance pine trees appear to 

 bear their main branches in circles or whorls, but closer 



412 



