68 
observations were intended to apply more especially to exogens, 
He explained that a circulation was set up by the act of growth in 
certain cells. This is called cyclosis. The cell, according to its par- 
ticular attribute, forms a particular kind of tissue, and transmits the 
fluid by a process which is styled ‘‘endosmose.”’ This action is easily 
produced by placing liquids of different densities on different sides of © 
a thin membrane, as a bladder. The one fluid attracts the other is 
a peculiar manner, so as to be able to support a considerable column 
of the mixed fluids above the level of the one which is attracted. 
Thus sugar and water attract water with great avidity; so does 
alcohol. This endosmose action is the vis a tergo—the force which 
raises the liquid from the soil to the upper part of the tree, and it is 
the force also which leads the ogygen to give place in the leaf to 
carbonic acid. But the question arise as to the channel through 
which it passed. The examples he had produced answered the 
question. It did not go through the bark, because that was re- 
moved in the one case and strangled in the other ; neither did it go 
through the outer layer of of woody tissue, but through the layers 
of tissue lying upon the duramen. It was probable that in its 
tran: mission upwards it prepared certain portions of a tree for the 
reception of used-up woody matter, which is taken away from the 
descending sap, and which is the formed matter eorresponding to an 
excretion in an animal; but as support is required, and the tree 
continues to grow, the formed material, as used up, provides that 
support, and thus the extension of an exogenous tree is, as far as 
size is concerned, unlimited. Describing the respiratory process of 
trees by which the carbonic acid in the atmosphere is kept at a 
minimum, and its place supplied by that which is necessary for 
animal life, Dr. Carpenter stated that this interchange of gas takes 
place through the stomata or so-called breathing pores which exist 
more or less on all leaves, there being as many as 160,000 in some 
instances on each square inch of surface; so that the dense foliage 
of a forest is one of the helps which a kind Providence has supplied 
to keep our atmosphere at its proper healthy standard. As forests 
are cut down it is man’s duty to provide distributed lungs, and the 
more the country is disforested the more necessary it is to secure 
an abundance of trees in our midst. After further explaining the 
interesting peculiarities of the circulation of sap in trees, Dr. Car- 
penter stated that it was between the bark and the wood that the 
new layer of tissue was first laid down, and thus might be perceived 
the reason why no new wood was formed below the cut on tree No. 
1 that he had referred to, or below the legature in No. 2.. Dr. Car- 
penter next referred to the lactiferous vessels in plants, the bark of 
exogenous trees, and the manner in which they may be destroyed 
by fungus growth and parasites. 
He showed a section of the great fir-tree which for many years 
had been a land-mark at the rectory at Sanderstead, which was now 
ee 
