LAYERS 



261 



In the apple and pear, roots form more readily when the 

 cuttings include a ' heel ' or small basal piece of wood from the 

 older branch on which the cutting originally grew. 



Hops are propagated by cuttings (p. 343), and the tubers of a 

 potato when very large or the variety a scarce one are sometimes 

 cut longitudinally so that each piece possesses an ' eye ' or 

 collection of buds which develops into a new plant when the 

 piece is placed in the ground. 



5. Layers. — The process of layering consists in bending and 

 pegging down a shoot of a plant into the soil as indicated in 



Fig. 92. From the bent por- 

 tion in the earth roots are 

 sooner a later emitted, after 

 which the shoots spoken of as 

 layers may be severed com- 

 pletely from the parent plant. 

 The mere bending and cover- 

 ing the shoot with moist warm 

 soil is sometimes sufficient to 

 induce the emission of roots, 

 but more generally one or other 

 of the various plans of ' tongue- 

 ing,' ' ringing,' and ' notching,' must be adopted to secure a good 

 formation of root. 



'Tongueing' is a term applied to the process of cutting an 

 oblique slit upwards as at a almost through the stem at a node. 

 ' Ringing ' (p) consists in removing a complete half-inch wide 

 ring of bark or tissues as far as the cambium of the stem : by 

 'notching' is meant the cutting of a V-shaped incision half 

 through the stem. All these devices and others which are 

 practised retard the flow of elaborated sap backward from the free 

 portion of the shoot above ground, and the consequent accumula- 

 tion of plastic material in the part of the shoot beyond the cut 

 tends to induce the formation of adventitious roots upon it. 



-Diagram illustrating method 

 b Ringed branch ; a tongued 



