170 THE PHYSIOLOGY OF PLANTS 



mented with, in case the operation should not be successful, 

 and he tries, therefore, to produce a stimulus at various places 

 on the shoot, by enveloping them with damp soil, but does 

 not separate the shoot from the parent plant. 



This process is termed layering. In certain cases this is 

 done (in the case of tall and rigid plants, especially if they are 

 valuable) by fixing some convenient receptacle to one of the 

 branches at a certain height and filling it with earth and 

 moss, which must be kept damp. After the branch has 

 become .rooted, it is separated below, the roots from the parent 

 plant. But all methods of layering in which the branch remains 

 in its natural position are less reliable than those in which the 

 branch is artificially bent. 



This may be taken as a guide for all cases of layering, and 

 the above-mentioned method of procedure is only to be re- 

 sorted to when regular layering cannot be employed. We 

 must remember, too, that the vigour of root formation in the 

 same species or variety of plant depends upoh the amount 

 of assimilated food material stored up in that portion of the 

 stem which is being stimulated by moisture. From what has 

 been said in the chapter on pruning',' we know that every 

 bend, notch, kink, or ring, cut on the shoot hinders the flow 

 of food matter, and causes the plastic material to be stored up 

 in the portion of the shoot above the wound. The bending of 

 the branch therefore is in itself a favourable preparation for 

 layering. 



The actual process of layering difiers for different plants; 

 even when the shoots are all near the ground. If such shoots 

 are not produced in sufficient numbers, they must be called 

 forth by cutting off the mother-plant close; above the soil, so 

 that strong lateral shoots may be developed. These can be 

 used already in their first year, when they are still herbaceous ; 

 they must then be bent outwards close to their insertion, and 

 the stump of the mother-plant and all the bases of the shoots 

 must be covered up with soil. If the branches have made 

 but few roots in their first year, it is advantageous to ring 

 the exposed places where they have been bent, and then to 

 cover them up again. The tips of the branches which have 

 now become woody are cut off, and the lateral shoots are 



