328 
which the bark is, have done. They prove against the descending 
circulation being solely confined to the bark layers, and show that it 
possesses the power of diverging into the layers of young wood until it 
passes the decorticated parts ; as much of it, at least, as enables the vital 
functions to be supported : but, no doubt, a great arrest of it takes place 
on the upper lip of the cut, or point of divergence from the bark cells to 
those of the cambium. 
There is, however, one important feature exhibited by those speci- 
mens, and also by those of diagram No. 2, namely, wherever the upward 
flow of sap has been arrested, adventitious buds have formed and pro- 
duced branches. It would thus appear that the peculiar kind of cells or 
lenticels, which form the basis of those elongating axes, are nourished 
and produced by the ascending sap, but whether that be truly the case, 
remains uncertain. The arrest of the upward flow of sap, and conse- 
quent greater accumulation of it at the lower lip of the cut, may cause 
a partial descent to take place, and thus give rise to the adventitious 
bud cells, but, certainly, I have never seen them produced above the 
upper lip of a partially decorticated stem, where roots will be produced 
if preparations be made to secure moisture and exclude light. 
No. 44. No. 4 c. No. 40. 
No. 4. 
The specimens agreeing with diagram No. 4 are curious. No. 4a 
is a portion of the branch of a weeping beech, which grew in a nearly 
downward vertical position from the bole of the tree to the earth, and 
was operated on to prove whether the denser sap would be affected by 
gravitation. It will, however, be seen, on examining the specimen, that 
this power has had very little influence. The newly formed tissue has 
increased for the most part in a vertical position from the apex to the 
