234 PROP A GA TION BY LA YERS. 



or shoot, and placing it under circumstances favourable for the pro- 

 duction of roots. The interruption is most successful when it takes 

 place immediately under a bud or joint, when the shoot is more or 

 less matured, and when it penetrates into the alburnum ; though, if 

 the alburnum is penetrated too far, the ascent of the sap will be inter- 

 rupted, and the supply to the buds or leaves will be insufficient to 

 develop them, or keep them from flagging. The descending sap may 

 be interrupted either wholly by cutting off a ring of bark, or partially 

 by a cut or notch, by driving a peg or nail through it, by a slit kept 

 open, by twisting the stem at a joint, by strangling it there with a 

 wire, by bending it so as to form an angle, by the pressure of a 

 stone laid on it, or by attracting it by heat and moisture. The latter 

 mode of causing a branch to protrude roots may often be observed in 

 nature, in the case of the lowest branches of trees and shrubs that rest 

 on the soil, and by their shade keep it moist, and, after some time, 

 root into it. Whatever mode of interrupting the sap be adopted, the 

 wounded part of the layer from which roots are expected to proceed 

 must be covered with soil, moss, or some other suitable material kept 

 moist, or it must be partially or wholly immersed in water. Layer- 

 ing, from the certainty which attends it, was formerly much more ex- 

 tensively employed as a mode of propagation than it is at present ; the 

 art of rooting cuttings being now much better understood, and being 

 chiefly adopted in house and in herbaceous plants; and layering being 

 confined in a great measure to hardy trees and shrubs, of which it is 

 desired to multiply plants that will speedily produce flowers, or that 

 cannot otherwise be so readily propagated. 



The state of the plant most favourable for layering is the same 

 as that most suitable for propagation by cuttings. The wood and 

 bark should be soft and not over ripe, and this is most likely to 

 be the case with lateral shoots produced near the surface of the 

 soil or in a moist atmosphere. Layers, like cuttings, may be made 

 either of ripe wood in the autumn or spring, or of growing wood any 

 time in the course of the summer ; the only condition, in the latter 

 case, being that the part of the shoot where the sap is interrupted be 

 somewhat mature, or firm in texture. 



Hardy trees and shrubs, with reference to layering, may be divided 

 into two kinds, those which, when cut down, throw up shoots from the 

 collar, that is, technically, which stole, such as most kinds of deciduous 

 trees and shrubs ; and those which do not stole, such as all the coni- 

 ferae. The former are planted and cut down, and layers made of the 

 young shoots which proceed from the collar ; while the latter are 

 either laid entirely down, and their branches extended along the 

 surface of the soil, and the extremities of all the shoots layered, or 

 such side branches as can be bent down to the soil are made fast there 

 by hooked pegs, and their shoots layered. When the shoots to be 

 layered are small, they are frequently twisted or slit through at the 

 point where the roots are to be produced ; but when they are strong 

 the knife is entered beneath a joint, and the shoot cut half through, 

 and the knife afterwards turned up half an inch or more, so as to form 



