SLIPS AND LAYERS. 247 



with a pick, and it is filled in with fine earth. This 

 method is adopted for growing pollards. 



Slipping with two year old wood is employed for 

 the small willows, the poplars, and the plane tree. 

 The slip is a branch of the current year, which is cut 

 off along with a portion of the older branch on which 

 it grows. It is shortened down to sixteen or twenty 

 inches, and the end is cut obliquely. It is then 

 pressed twelve or sixteen inches into the ground. 

 When the soil is light it is pressed in at once ; other- 

 wise a hole is made with an iron bar, or the soil is 

 loosened so as to prevent the bark from peeling off. 

 The process is facilitated if the slip is pressed in 

 obliquely. Slipping is often performed in nurseries ; 

 here the slips are planted in regular lines after 

 thoroughly loosening the soil. 



Propagation by layers consists in bending down a 

 young sapling in such a way as to lay it against the 

 ground without breaking it off. It is kept in this 

 position by means of strong wooden hooks driven 

 into the ground, and soil is thrown over the young 

 branches, the extremities of which are turned up 

 vertically. These branches soon take root, and 

 when they are able to nourish themselves indepen- 

 dently, they are severed from the parent stem. This 

 is generally done at the end of two or three years. 

 If the tree is too thick to bend without breaking, an 

 incision is made for the purpose, which is covered to 

 prevent the wood from drying up. This method 

 may be used to fill up very small blanks ; but it is 

 better to plant, which permits of the introduction of 

 valuable trees where they do not exist. 



