1901.] NATURAL SCIENCES OF PHILADELPHIA. 363 



is clearly apparent. The tree could scarcely keep a mass of foliage 

 in healthy condition wholly to the ground if it adhered strictly 

 to the acute-angular method that marks the upper growths. 



So far we may trace the effort for individual benefit in the direc- 

 tion changes, but that conditions of environment are active forces 

 in the work may well be doubted from the fact of great variation 

 in the degrees of curvature. 



It has already been stated that the observations were made on 

 my own grounds. Comparing, however, trees of my own with 

 other.s of the same species on neighboring properties, we find wide 

 divergencies. In some trees of the same species there will be few 

 illustrations of curving, while in others nearly every large branch 

 will take on an arcuate form. This fact is illustrated in Plate 

 XVI of Magnolia acuminata. The two trees are within thirty 

 feet of each other. The one on the right shows considerable 

 incurving. The upper branches have retained their original 

 angular divergence, and the bend toward the horizon as age 

 advanced has been gradual ; only a few at the base and on the one 

 side have reached that point. We can see that if this tree had 

 wholly lost the recurving power we should have a fastigiate indi- 

 vidual, closely imitaling a Lombardy Poplar in form. But the 

 one on the left took early to recurving, and to such an extent that 

 it seemed to the good of the tree that these should ultimately 

 incurve in order to afiord room for a healthful branching devel- 

 opment. 



"With all these individual variations there is still a general char- 

 acter assumed by each species, by which it may be distinguished as 

 well as by the characters derived from leaves, flowers or fruits. 

 In Quereus paludris, for instance (Plate XVII), there is little dis- 

 position to curvature in the decumbent branches. They bend very 

 close to the main trunk. They commence to diverge when about 

 five years old, and the continuously increasing degree of divergence 

 can be seen at a glance. This character will vary more or less in 

 different trees, but there is almost always enough in evidence to enable 

 one to distinguish the Pin Oak from other species. The Scarlet Oak, 

 Quereus coccinea, rarely shows any disposition to curve mature 

 branches. A representation of this species is given on the right 

 hand of the Pin Oak (Plate XVII). But hei-e we may note again 

 that there is no necessity for it, as the original angle of divergence 



