224 ON VEGETABLE ORGANOGRAPHY AND PHYSIOLOGY. 
reply, in the hope of showing that you have argued from assumed, 
rather than from incontrovertible, premises; and that, if you will quit 
those uncertain positions, and take purely neutral ground, are-investi¬ 
gation will bring you much nearer to the goal of nature and true 
philosophy. 
Had we leisure just now to turn over the book, we could from thence 
muster sufficient answers to everything you have boggled at ; but 
besides the want of time, we feel it unnecessary to reply to every par¬ 
ticular (involving too much egotism) which seems to thwart your pre¬ 
viously settled opinions concerning the nature, motion, and powers of 
the sap; for, so long as you believe that the sap is elaborated in, 
instead of by, the leaves, and attribute all accretion to its organisable 
properties, so long must your mind be “ steeled proof” against the 
reception of a contrary doctrine. And what proof, pray, has yet been 
had that the sap regularly descends, or that it is organisable ? Can 
you or any one else bring forward a single indubitable proof of such a 
fact? You may think it f<r more philosophical, and more in consonance 
with the phenomena of organised existence, to admit at once a prin¬ 
ciple of regularity of movement, than to consider that those wonderful 
developments are effected by any process bordering upon being fortui¬ 
tous ; ” but true philosophy attends only to facts, and can admit no 
principle of imaginary movement, how plausibly regular soever it may 
seem to be. 
You refer us to the swelling of a stem above a wound or ligature, as 
a proof of the descent of the sap: as well may you assert that the 
descent of the roots into the ground is a proof of its subsidence, for they 
are exactly similar movements. But we have, as you know, advanced 
so much already on this circumstance in our book and elsewhere, to 
show that it is not owing to any constant or periodical descent of the 
sap alone , that any further disquisition would be nauseating, as well 
as fruitless, if what has been already said fails to convince. 
Although you find no difficulty in accounting for the extension of 
new wood and bark from the upper side of a wound on the stem of a 
tree, you seem to be puzzled to find a good reason for its increasing 
from below. You believe that the increase above is caused by an 
accumulation of the descending elaborated sap, while you do not seem 
to consider that the ascending current has any such expanding power, 
attributing the increase there to some accommodating agency of the 
vitality of the system. This we cannot gainsay, because we know of 
no accommodating power, save the expansion of the vital membrane, 
which is always ready to repair a fracture in any part, or in any direc- 
