20 



GENERAL BOTANY 



'alse whorls 



immediately below it, by that portion of the terminal twig which 

 bore latent buds and is hence devoid of branches (Fig. 10, ) 

 Since but one false whorl of branches is produced each season 

 in the manner described above, the trunk of an adult pine tree 

 presents a series of false whorls of branches from base to apex, 



separated by smooth 

 portions of the trunk 

 (Fig. 10, 6). These 

 smooth, branchless por- 

 tions of the trunk are 

 not internodes, as they 

 are sometimes thought 

 to be, but rather rep- 

 resent those portions 

 of the terminal twigs 

 of each season where 

 the latent buds failed 

 to produce branches. 

 Since the branches at 

 the apex of the tree are 

 younger and so shorter 

 than those toward the 

 base, the result is a 

 pyramidal tree with a 

 strong central excur- 

 rent trunk. 



The needle leaves 

 and reproductive cones 

 are always produced 

 by buds at the ends of the lateral branches, and on account of 

 their spiral arrangement they are so placed as to be admirably 

 exposed to the sunshine, which aids the leaves in their food- 

 making, and to the wind, which helps to scatter the winged 

 seeds of the pine cones. The body plan and the method 

 of bud growth, therefore, combine in the pines to produce a 

 tree of great beauty and of nice adaptation to environmental 

 conditions. 



False 

 whorl 



FIG. 10. Pine trees illustrating the erect type 



a, a young pine ; b, a mature pine. Observe the ex- 

 current trunk, the false whorls of branches, and the 

 pyramidal form. Consult the text for the main fac- 

 tors concerned in the seasonal growth (1-7) and the 

 development of these external features of the pine 



