206 



EFFECTS OF FROST ON TREES. 



lived and flourished ; those unremoved died 

 that summer of blight. This limestone soil 

 on which the pear blights, so far as I have 

 seen it examined, is fertile on the top, and 

 a very close solid clay for some four feet 

 under. This clay becomes so dry in the 

 latter part of the season, that in many 

 places it cracks, and makes fissures of from 

 one-fourth to an inch wide. The cause of 

 the blight seems to be, the moisture kept to 

 the surface by the clay, induces rapid growth 

 in the fore part of the season; and when dry 

 hot weather sets in, the upper fertile stra- 

 tum dries, and suddenly withholds the pro- 

 per nourishment ; or in the fall the mois- 

 ture is retained, when early autumnal rains 

 occur, and late growth is caused, and the 

 frozen-sap blight follows. The remedy, I 

 suppose, is to cut through the clay, and 

 make a connection of friable soil with the 

 under strata, which is generally porous, 

 and from the great depth at which I have 

 seen roots growing, I judge when once 

 through the upper strata, roots flourish well; 

 but as I intend to have it tried at Loydsville 

 the coming year, I may hereafter give a 

 better opinion on the subject. E. Nichols. 



Walhonding, Ohio, Sept. 1. 1S47. 



Remarks. — (a) Our correspondent mis- 

 takes our view. M. Morren's first apho- 

 rism is, that no organ of plants is rent by 

 the action of cold, except in a few rare 

 cases, when the cavities of the cellular tis- 

 sue yield to the effect of the dilatation of 

 the liquid. Our remark was intended to 

 call attention to the common and well 



known instances of the rending of the 

 trunks of trees in the northern states, the 

 result, as we believe, of the expansion of 

 sap vessels by freezing. We are very well 

 aware that death does not usually ensue 

 when this happens to perfectly hardtj trees, 

 but it does when the tree is rather tender. 



{h) Why certain trees are hardy in their 

 nature, and others tender, physiologists 

 have as yet been able to give no explana- 

 tion, other than a particular constitution 

 adapted to the climate they naturally inha- 

 bit. A potato, which is a tropical root, re- 

 tains this delicacy of constitution, and there- 

 fore freezes much more quickly than an 

 apple or a beet, both of which are natives 

 of cold climates, and have constitutional 

 or vital capacity of resisting frost. The 

 trunk of the mahogany tree is one of the 

 firmest, closest, and least sappy known, yet 

 this tree will not bear the least exposure to 

 a northern winter, while the poplar and the 

 willow, counted among the softest wooded 

 trees, full of juices, will bear the winters 

 even of the frigid zones. 



The important fact that we intended to 

 convey in the note referred to by our cor- 

 respondent, is that of two given trees of the 

 same species, only partially hardy, or which 

 are liable to injury in winter, that which 

 had thoroughly elaborated its juices by an 

 early growth well matured, is, as experience 

 has repeatedly proved, in a much better 

 condition to resist the action of frost, than 

 another which has made a late growth, and 

 is more or less replete with watery fluid or 

 crude sap. — Ed. 



Varieties of Pears. — T. Rivers, of the 

 celebrated Sawbridgeworth nursery, Eng- 

 land, has about nine hundred varieties of 

 the pear under trial. Robert JVIanning, of 



Salem, Massachusetts, had about eight hun- 

 dred. Probably not forty of all these are 

 fully first rate, or worthy of extensive cul- 

 tivation. 



