205 
emission of roots by layers of trees of different species which 
do not readily emit roots^ by the following means, having 
detached the tongue of the layers from the branches in the 
usual manner. Soon after Midsummer, when the leaves upon 
the layers had acquired their full growth, and were, according 
to my hypothesis, in tlie act of generating the true sap of the 
plant, the layers were taken out of the soil, and I found that 
those of several species of trees did not indicate any disposition 
to generate roots, a small portion of cellular bark only having 
issued from the interior surface of the bark in the wounded 
parts. I therefore took measures to prevent the return of the 
sap through the bark, from the layers to the parent trees, by 
making, round each branch, two circular incisions through the 
bark, immediately above the space where the tongue of the 
layer had been detached; and the bark between these inci- 
sions, which were about twice the diameter of the branch apart, 
was taken oft’. The surface of the decorticated spaces was 
then scraped with a knife, to i)revent the reproduction of the 
bark, and the layers were recommitted to the soil ; and at the 
end of the month I had the pleasure to ol>serve that roots had 
been abundantly emitted by every one. In other instances, I 
obtained the same results by simply scraping off, at the same 
season, a portion of the bark, immediately at the base of the 
tongue of the layers, without taking them out of the ground. 
By the preceding mode of management, the ascending fluid 
is permitted to pass freely into the layer, to promote its growth, 
and to return till the period arrives at which layers generally 
begin to emit roots ; the return of tlie sap through the bark, is 
then interrupted, and roots are, in consequence, emitted; and 
I entertain little doubt that good plants of trees, of almost every 
species, may be thus obtained at the end of every season. I 
wish it, however, to be understood, that my experiments have 
been confined to comparatively few species of trees ; and that 
I am not much in the habit of cultivating trees of difficult 
propagation. 
197 Oniox, Culture of. Every bulbous-rooted plant, and 
indeed every plant which produces leaves, and lives longer than 
one year, generates, in one season, the sap, or vegetable blood, 
which composes the leaves and roots of the succeeding spring ; 
and when the sap has accumulated during one or more seasons, 
203, AUCTARIUM. 197» Knight’s Papers, p. 181. 
