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tablished theory, bear out Dr. Schleiden’s views in a remark- 
able manner. It is true the newly-formed tissue extended 
from the upper lip of the cut chiefly in the downward direction, 
and that very little appeared on the lower lip. But the 
train of reasoning I adopt from these circumstances is that 
of Dr. Schleiden. The flow of sap by endosmotic process from 
cell to cell, was interrupted by the alburnum and cambium 
being cut across on the pillar which was laid bare. It there- 
fore diverged’ laterally, and followed its natural upward 
course, on the three pillars where no laceration had been made, 
which accounts for no growth taking place on the lower lip. 
On the portion of stem above the cut, a greater degree of 
formative energy accrued, in consequence of the interruption 
the endosmotic process met with below. The tissue thus 
formed would rather extend itself on the vacant space under, 
i.e., the bare pillar, than upwards, where endosmosis was less 
vigorous, in consequence of many of the cells being filled with 
sap of greater density. In this manner it continued to grow 
until it reached the lower lip of the cut, where its downward 
course was obstructed, when it spread in a lateral direction 
over the surface of the lip, as well as upwards, until the bare 
surface became covered over. During the whole process it 
did not occur to me, that the young wood was formed by a 
returning bark-sap. ‘The growth seemed gradual and not 
periodical. The young tissue taking a lateral and upward di- 
rection when it met the lower lip, shows that, although the 
tendency be downwards, it will alter. 
«¢ A remarkable example of the permeability of the tissues 
of plants has farther been proved through this experiment. 
From knowing the heart-wood was dead at the part of the stem 
which was operated on, I was desirous to ascertain whether it 
continued so to the apex of the tree, which I had some reason 
to suppose it did, from having about four years ago observed 
a small portion of the top shoot dead. I, however, found the 
heart-wood full of sap, and apparently very healthy, in a piece 
