REPRODUCTIVE POWER OF TREES. 



37 



hollow below, and those on the upper slopes of a high 

 mountain are commonly starved and stunted in com- 

 parison with the vigorous forest lower down. (See PI. 

 XVII.) The Western Chinquapin, which reaches a 

 height of 150 feet in the coast valleys of northern 

 California, is a mere shrub 

 at high elevations in the 

 Sierra Nevada. The same 

 thing often appears in passing 

 from the more temperate re- 

 gions to the far north. Thus 

 the Canoe Birch, at its north- 

 ern limit, rises only a few 

 inches above the ground, 

 while farther south it becomes 

 a tree sometimes 120 feet in 

 height. 



THE REPRODUCTIVE POWER 

 OF TREES. 



Another matter which is of 

 the deepest interest to the Fl : ; as-western Yellow H , m 



mixture with other trees. Hat- 

 forester is the reproductive head Valley, Montana. 



power of his trees. Except 



in the case of sprouts and other growth fed by old 

 roots, this depends first of all on the quantity of the 

 seed which each tree bears; but so many other con- 

 siderations affect the result that a tree which bears seed 

 abundantly may not reproduce itself very well. (See 

 fig. 30.) A part of the seed is always unsound, and 

 sometimes much the larger part, as in the case of the 

 Tulip Tree. But even a great abundance of sound seed 

 does not always insure good reproduction. The seeds 



