Propagation by Layers and Grafts. 269 



employed by the gardener ; who sometimes varies it, by not 

 detaching the bud from the parent stock, but by bending a 

 branch into the earth, and letting it be partly supported by the 

 juices of its parent, until it has put forth roots for itself. This 

 j s termed propagating by layers. 



But there are many cases in which it is desirable not to trust 

 to the power which the bud may possess of forming roots for 

 itself; and advantage is then taken of the tendency which the 

 growing parts of plants have to adhere and become united to 

 each other. Such adhesions not unfrequently take place from 

 natural causes. Thus, if two branches, either of the same or 

 of different trees, be lying across each other, in such a position 

 as to rub against one another when moved by the wind, the 

 bark will be worn off from each, and a fluid will exude from 

 the wounds, which will be in time converted into solid tissue. 

 This is capable of conveying sap from one branch to the other ; 

 for a tree which has been thus united (for the sake of experi- 

 ment) to two others, and has been thus cut off from all com- 

 munication with the soil, has continued to live, without any 

 other supply than that which it has derived through these trees. 

 This natural adhesion of vegetable tissue is well seen in the 

 ivy ; the branches of which often interlace and graft together 

 in various places, until the whole forms a rude net-work, en- 

 closing the trunk of the tree on which it has climbed. 



Now the gardener imitates this process, when he wishes to 

 supply the separated buds of a tree or plant which he is de- 

 sirous of propagating rapidly, with nourishment ready to be 

 elaborated by its leaves. He chooses a stock, or stem deprived 

 of its own buds, and cuts off its top in a sloping direction, so 

 as to expose a large surface of wood and bark. He cuts the 

 lower end of the young branch, or graft, in a similar manner, 

 and then fixes them together, taking especial care that the bark 

 and wood of the one should meet and join with the bark and 

 wood of the other. If the operation succeeds, the stock and 

 the graft become so completely united together, as to form in 

 time but one tree, in which all mark of the original separation 

 has disappeared. The stock draws up from the soil the fluid 

 which the leaves of the graft require ; these obtain carbon 

 from the air, and elaborate the crude sap into proper juice, a 



