207 
any degree of precision, pronounce what portion of his blossoms 
will afford fruit. If a larger part of it than he has been led 
to anticipate prove abortive, he generally attributes its falling 
off to something which he calls a blight, and which he sup- 
poses to be the operation of some unknown noxious quality in 
the atmosphere, during the season in which his trees have been 
in blossom. 
jNIany circumstances have at different periods come under 
my observation, which have led me to draw a different conclu- 
sion, and to believe that whenever a very large portion of the 
well organized blossom of fruit trees falls off abortively, in a 
moderately favourable season, the cause of the failure may 
generally be traced to some previous check which the motion 
and operation of the vital fluid of the tree has sustained. 
It is well known that the bark of oak trees is usually stripped 
off in the spring, and that in the same season the bark of other 
trees may easily be detached from their alburnum, or sap- 
wood, from which it is, at that season, separated by the inter- 
vention of a mixed cellular and mucilaginous substance; this 
is apparently employed in the organization 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 occur, tlie bark of the trunk or main stem 
of the oak tree becomes again firmly attached to its alburnum, 
from which it cannot be separated 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 
dissimilarity 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 
20t, ACCTAKICM. 
