106 APPLICAriON OF PRIKCIPLES. 



stance of Vines that are forced early not setting theii 

 fruit well, when their roots are in the external border 

 and unprotected by artificial means ; and to the same 

 cause is often to be ascribed the shrivelling of grapes, 

 which, as we all know, most commonly happens to 

 Vines whose roots are in a cold and unsunned bor- 

 der. 



Mr. Eeid of Balcarras has, indeed, shown that one 

 of the causes of canker and immature fruit even in 

 orchards is the coldness of the soil. He found that, in 

 a cankered orchard, the roots of the trees had entered 

 the earth to the depth of 3 feet; and he also ascertained 

 that, during the summer months, the average heat of 



that season, separated, by the intervention of a mixed cellular 

 and mucilaginous substance ; this is apparently employed in the 

 organisation of a new 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, oeom-, the 

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

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

 rated until 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 trees 

 appear to be affected to the same extent by similar degrees of 

 cold. Their blossoms, like those of the Oak, 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 dissimilarity of constitution.'' (fibrt. Trans., vi 

 229.) 



