256 On the Emission of Roots from Layers. 



When a layer is prepared, and deposited in the ground, 

 the progress of the sap, in its descent towards the original 

 roots, i s intercepted upon the side where the partially de- 

 tached part, or tongue, of the layer is divided from the 

 branch ; and this intercepted sap is, in consequence, gene- 

 rally soon employed in the formation of new roots. But 

 there are many species of trees which do not readily emit 

 roots by this mode of treatment ; and I suspected that, 

 wherever roots are not emitted by layers, the sap, which de- 

 scends from the leaves, must escape almost wholly through 

 the remaining portion of bark, which connects the layer with 

 the parent plant. I therefore attempted, in the last and the 

 preceding spring, to accelerate the 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 the 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 

 incisions, which were about twice the diameter of the branch 

 apart, was taken off. The surface of the decorticated spaces 



