On Protecting the Stems of Fruit Trees from Frost 229 



It is well known that the bark of Oak trees is usually 

 stript off in the spring, and that in the same season the bark 

 of other trees may be easily detached from their alburnum, 

 or sap wood, from which it is, at that season, separated by 

 the intervention of a mixed cellular and mucilaginous sub- 

 stance ; this is apparently employed in the organization of 

 a hew layer of fibre, or inner bark, the annual formation of 

 which is essential to the growth of the tree. If, at this period, 

 a severe frosty night, or very cold winds, occur, the bark of 

 the trunk, or main stem, of the Oak tree, becomes again 

 firmly attached to its alburnum, from which it cannot be se- 

 parated till the return of milder weather. Neither the health 

 of the tree, nor its foliage, nor its blossoms, appear to sustain 

 any material injury by this sudden suspension of its functions ; 

 but the crop of Acorns invariably fails. The Apple and Pear 

 tree appear to be affected to the same extent by similar 

 degrees of cold. Their blossoms, like those of the Oak, 

 often unfold perfectly well, and present the most healthy and 

 vigorous character; and their pollen sheds freely. Their 

 fruit also appears to set well ; but the whole, or nearly the 

 whole, falls off just at the period when its growth ought to 

 commence. Some varieties of the Apple and Pear are much 

 more capable of bearing unfavourable weather than others, 

 and even the Oak trees present, in this respect, some dissimi- 

 larity of constitution. 



It is near the surface of the earth that frost, in the spring, 

 operates most powerfully, and the unfolding buds of Oak 

 and Ash trees, which are situated near the ground, are not 

 unfrequently destroyed, whilst those of the more elevated 

 branches escape injury ; and hence arises, I think, a proba- 



