NATURAL SCIENCES OF PHILADELPHIA. 351 



struck observers that the trees were all pretty much of one age. 

 Here we see a piece of forest in which the trees might be one hun- 

 dred years old; there another perhaps fifty; and again young 

 ones of from ten, twenty, and so on. They are, however, generally 

 of one age, and though there are some 3^ounger trees of various 

 ages scattered through, the great bulk of each forest started from 

 the seed in the same season together. It was remarkable that of 

 the immense amount of seeds annually produced by forest trees, 

 how few of them grew. In the forests we found, as a rule, few 

 seedlings, and though the boundaries of a piece of woodland might 

 not be under cultivation, so as to destroy any vegetating seeds, 

 the forest boundaries were seldom enlarged in any gradual way. 

 In the woods about Philadelphia, the American white oak was not 

 particularly abundant. Here and there were a few trees in almost 

 every piece of wood ; and though the trees bore acorns onl}^ every 

 other 3'ear as a rule, yet in the bearing season they were more 

 abundant than in most other species ; yet young ones were so 

 scarce that if the forests were cut away three years ago, the suc- 

 cession would not be remarkable for Quercus alba. But in 18Ti2 

 the productive year for the acorns there was something so favor- 

 able to their vegetation that seedlings now abound in these woods, 

 and if the growing timber were now cut away, so as to give these 

 seedlings a fair chance for life, the future forests of this part of 

 Pennsylvania would be especially of white oak as distinctly a 

 white oak region as some parts of our country are fixmous for their 

 pines. We see, however, from this that it is only at special times 

 and under special circumstances, that seeds grow to any great. ex- 

 tent in our comparatively favored forest region, and we can un- 

 derstand better the fact referred to, of forests generalh' having the 

 mass of their timber trees about of one age. 



Carr3ang these facts with us, we may understand some of the 

 phenomena accompanying the forest distribution in the far west. 

 Along the Rock}' Mountain range, as well as in the Wahsatch and 

 Uintas, the prevailing deciduous tree, or rather shrub (for it is 

 scarcely a tree), is what has been supposed to be a variety of Quel-- 

 cus alba (var. Gunnisonii) hy some, and by others a variety of Q, 

 Douglassii (var. 7ieo-3Ie:ricana)^ but wiiich 1 believe Mr. AV'atson 

 has recently made a distinct species under the name of Q. polymor- 

 ph a^i an excellent name when the many varied forms are consid- 

 ered. It is unusual to find it growing in dense thickets, Gene- 

 ralh' it is in clumps of from five to twenty-five or more feet in dia- 

 meter. Each clnmp has evidently started from one seed at some 

 one time; and from one stem, underground suckers proceeding a 

 few inches each season, have made the mass of stems as we see 

 them. One could almost tell the age of the clump by the graded 

 heights of the mass, the tallest of course being in the midille, and 

 the outside often but a few inclies, being the most recent growtli. 

 In this way the mass of varied characters becomes very striking. 



