ON PEARS. 
Ill 
portion of it. The limb is constricted, and is nearly one quarter smaller than the adjacent 
parts above or below. This constricted portion appears so perfectly dead and dry, that it 
seems impossible for the sap to pass through it and reach the vigorous and living portion 
beyond; which is not only bearing large leaves but also fruit, which is also equally as 
large and promising as that upon any of the unaffected limbs. 
The effect of the disease as exhibited in very numerous instances, is much the same as 
that which follows from ringing a branch; a process by which the circulation, as is main¬ 
tained, is interrupted. Its descent to the root is at least partially prevented, by which 
there is an accumulation at all times of nutritious fluids in the limb above the removed or 
injured bark and wood. The constriction where the disease is seated is mechanically 
arrested, however, with the ascent and descent of the sap; for here it is evident, by the 
dry state of this portion of the limb, that its vessels are nearly impervious; and after a 
short time they become entirely so—the dis¬ 
ease passing from outside to inside, and not in 
the opposite direction. The circulation, there¬ 
fore, is sustained by the interior. It would 
seem from an inspection of the dying branches 
that it is almost impossible, in many instances, 
for the sap to pass along the limb; still, there 
is no doubt that this it does so long as a green 
leaf appears. 
The following cuts exhibit the facts we have 
stated; and it may, if followed out, throw new 
light upon the circulation of sap, and of the 
nutrition of vegetables. 
Fig. 1. Part of a blighted branch of an 
apple tree, which was taken from the garden 
of E. P. Prentice, Esq., of Albany. 
c, Dead bark and wood ; b , living bark and 
newly formed wood; c, constricted portion of 
the stem, and dead upon the outside ; e, inte¬ 
rior of the stem, showing signs of life ; f, liv¬ 
ing and luxuriant growth of part of the branch. 
In this example there is quite a thickened 
state of the branch at a , which in the speci¬ 
men, is strongly contrasted with the part be¬ 
yond the dead portion ; as it is about ^ thicker 
by the formation of new wood since it was 
attacked by the blight. Most of the new 
growth has taken place since the time when 
a branch usually acquires the length of stem 
for the season. In the bark, or immediately 
Fig. 1. 
