60 PB ACTIO AL GUIDE TO GARDEN PLANTS 



soil, a small peg, or a pebble, and this induces a callus to form and 

 roots to develop more quickly. Where the branches to be layered are 

 near the ground, as in Carnations, Strawberries &c. there is little 

 dif&culty in performing the operation. Occasionally, however, branches 

 of trees a few feet above the ground have to be layered. They must 

 be carefully bent down, firmly pegged at the point of contact, and 

 covered with soil. As a rule when the branches are fleshy or woody 

 they may be notched or slit, but they are also simply twisted so as to 

 bring the cells closer together at the twist, and thus arrest the down- 

 ward course of the elaborated sap. 



Principle of Layering. — Layering is practised on the principle that 

 any injury which prevents or checks the return of the elaborated sap 

 down the stem greatly facihtates the production of roots. This check 

 is brought about by slitting the stem, removing a portion of the bark, 

 notching &c. on the under side. As in a cutting, a ' callus ' is formed 

 on the cut surface by the returning sap, and roots are eventually 

 developed. 



Sometimes, instead of making an incision in the stems, a ligature of 

 some kind, say wire, is bound round it tightly. This checks the return 

 of the sap, and the stem above the ligature increases in size. If placed 

 in the soil roots will be emitted, but if exposed to the air the effect in 

 the case of fruit trees is generally seen in much larger and finer fruits. 



6. Propagation by dividing the Rootstock 



In the case of hardy herbaceous perennials (i.e. plants which live 

 for several years, but the stems of which die down annually) dividing 

 the roots in autumn or spring is found to be an easy means of propaga- 

 tion. The more carefully the work is done, the less injury is caused, 

 and the sooner the plants recover. Chopping up with a spade in the 

 case of Phloxes, Perennial Sunflowers, Larkspurs &c. is not to be 

 recommended, as too much needless damage is caused thereby. 

 Wherever shoots spring from the base or around the old rootstock 

 they may be carefully detached either with the fingers or a sharp 

 knife, and if inserted in good soil and kept shaded for a time, will 

 produce good plants. 



7. Propagation by Suckers 



Many plants throw up from the root numerous leafy branches 

 called suckers. It is often found useful to detach these carefully by 

 means of a sharp knife or other instrument with as much root as 

 possible attached. By transplanting to a shady place, they soon 

 recover and are then practically established plants leading an indepen- 

 dent life. 



