THE FALL OF THE LEAF 121 



statement holds true in regard to our cone-bearing evergreen 

 trees, such as pines, spruces, and the like. But the impossibility 

 of absorbing soil water when the ground is at or near the freez- 

 ing temperature would cause the death, by drying up, of trees 

 with broad leaf surfaces in a northern winter. And in countries 

 where there is much snowfall, most broad-leafed trees could 

 only escape injury to their branches from overloading with snow, 

 by encountering winter storms in as close-reefed a condition as 

 possible. For such reasons our common shrubs and forest trees 

 (except the cone-bearing, narrow-leafed ones already mentioned) 

 are mostly deciduous,- -that is, they shed their leaves at the 

 approach of winter. There are, however, in the eastern United 

 States a few species of broad-leafed evergreen trees and large 

 shrubs, such as the live oak, some Rhododendrons, the mountain 

 laurel (Kalmia), and the hollies. Along the Pacific coast there 

 are many more forms, including five fairly common species of 

 evergreen oaKs, the beautiful Arbutus, and the manzanitas 

 (Arctostapli ylos\ 



Looking somewhat closelv into the matter of deciduousness 



o *) 



of the trees and shrubs of temperate climates (not including the 

 coniferous species), one finds that they may be classed as follows : 



"1 A, \vinter deciduous 

 1. Leaves simultaneously deciduous . . i- T 



j B, summer deciduous 



C, leaves some of them 



II. Leaves not simultaneously deciduous 



lasting two years or 



more 



(evergreen) D, leaves lasting more 



than- one year but less 

 j than t\vo 



The only one of the four subdivisions which shows fairly con- 

 stant leafage at all seasons is the one designated as C. Leaves 

 of the subdivision D often fall when about fifteen months old, 

 so that the tree is unusually leafy during the three months 

 when the new leaves are developing to their full size, but before 

 the old ones begin to fall. It is a noteworthy fact that in many 



O J v 



species of broad-leafed evergreens, for example the ilex oak, the 



