30 TREES OF MASSACHUSETTS. 



should take place, the woods must contain trees of various kinds 

 sufficient to supply the whole surface with seed. When this is 

 the case, a wood of one kind will usually be found full of little 

 trees of other kinds. "Upon clearing off the old growth, the 

 undergrowth, which has been kept from the sun, shoots up 

 with astonishing rapidity." * That portion of it which is most 

 unlike the previous growth, finds plentiful nutriment, while the 

 proper food of the previous forest has been exhausted, and the 

 woods naturally change their aspect. 



The forests, as has been stated, form or improve a soil. This 

 they do by their annual deposit of leaves, and by rendering the 

 ground accessible to air, by the action of their roots. Both 

 operations are essential, and aid each other. If the leaves were 

 not deposited, the surface of the ground would speedily become 

 dry and hard, and the radicles which had previously pervaded 

 it, would be exposed to cold in winter, and to heat and drought 

 in summer. The covering of leaves protects against all. By 

 them the superficial portions are kept moist and soft, and per- 

 meable by the delicate radicles, and these are protected, while 

 they are made readily accessible to moisture from rain charged 

 with carbonic acid, and to air and a tempered warmth. The 

 covering of leaves thus secures all those circumstances which 

 are most favorable to vegetable growth. It is, therefore, justly 

 enumerated, by some of my correspondents, among the things 

 most unfavorable to the growth of trees, to gather the leaves 

 together, as is frequently done, either to burn them or to add 

 them to the compost heap. This is bad economy. It is double 

 robbery. It is taking from the forest what belongs to it, and is 

 almost essential to it, and it is spreading, with loss of time, upon 

 the present cornfield, what, left undisturbed, is at once a store- 

 house and laboratory of manure for the future cornfield, on 

 which it is already spread and spreading itself. 



The other circumstances enumerated as particularly unfavor- 

 able to the growth of trees, are browsing, pruning, a thin soil, 

 exposure to sea breezes, to high winds, and to frosts. 



* Mr. A. Bacon, of Natick. 



