28 THE TREES OF AMERICA. 



numerous cases of this kind, I may mention the experiments of Mr. Buckman, a 

 gentleman whom I have before alluded to in this work, upon the Bignonia, — fine 

 large vines of which he has growing, and flowering from year to year, in a sit- 

 uation where they invariably die if not protected in their infancy. 



Every one is familiar with the fact, that blight is often attributed to the wind, 

 and that it is said that the wind poisons the plants. Thus a writer, in accounting 

 for Mr. Tudor's success in raising fruit at Nahant, where his trees are protected by 

 open fences, says, that these fences " sift the wind," — that is, take the poison out 

 of it, we suppose. A scientific friend remarks to the author, that a neighbor of 

 his has a field which was much exposed to the east wind, upon which repeated 

 trials to raise wheat had been made, but in vain, as it was all blighted in flower, 

 until a few rows of trees were planted upon the windward side ; since then there 

 has been no difficulty in raising a good crop. 



The statement, then, may be made in brief, as follows : Mr. Tudor's success 

 in raising fruits and flowers, &c., at Nahant, by protecting them with open 

 fences, depends upon the fact, that these fences, besides shielding them from 

 mechanical violence, prevent the rapid abstraction of vital heat, by retarding 

 the motion of the wind, and perhaps, also, by breaking the currents, causing 

 them to return upon each other, and in this way contributing to the same result. 

 Further, they may operate, as Mr. Tudor himself suggests, in shielding them 

 from the efiects of warm winds in winter, which cause sudden changes to the 

 opposite extreme, and may in this manner, in some cases, cause them to " win- 

 terkill." 



The abstraction of moisture is subject to the same laws, and tends to the 

 same end, — the destruction of life; it also takes with it vital heat. Elec- 

 tricity, no doubt, plays its part also, and the chemical changes which are 

 constantly going on in plants must of course be directly affected by the 

 same causes. 



Whatever be the theory we adopt to explain the fact, it is sufficient for our 

 purpose that trees protect vegetation, and by their agency a barren soil may be 

 made to yield food for man and beast. Their effect in preventing drought, the 

 permanent drying up of ponds and streams, and equalizing the flow of rivers. 



