Theory of Propagation. 47 



a new plant. If the branch be long and pliable, several plants 

 may be made to spring from it. This is called a serpentine 

 layer, because the branch takes a serpentine direction, being 

 made alternately to sink below and rise above the ground, as 

 often as it is intended that new roots and stems should spring 

 from it. Layers are sometimes made in arches, by burying the 

 extremity of the branch only ; the separation is afterwards made 

 when the branch has struck root ; this mode is particularly suited 

 to the Raspberry, and every species of brambles. The Ana- 

 plastic operations of modern surgery bear a slight resemblance 

 to this plan ; they consist in covering the skeletons of noses, 

 patching burnt cheeks, &c, &c, by taking a piece of the integu- 

 ment from one part of the face, generally the forehead, and filling 

 up as they require it ; exactly resembling a tailor's mode of patch- 

 ing cloth, except that a small link always remains to nourish the 

 new skin until its vessels have struck into the surrounding parts, 

 when the connection is dissolved. There is a class of aerial 

 roots which fall to the ground, and taking root, spring up into 

 trees, which, in turn, send out shoots that obey the same law, 

 and so on ad infinitum ; the whole still retaining their connection 

 with the parent trunk. Of this kind is the Screw Pine, a palm- 

 like tree, often seen in our conservatories ; the Mangrove, of 

 the tropics, and the famous Banyan, which alone makes a forest. 

 Humboldt managed to take to Europe a great number of rare 

 and curious plants, by placing the layers in baskets filled with 

 earth, instead of at once in the ground ; when ready, he cut the 

 connecting branch, and thus had his prize in a portable form. 

 The latter end of February, and the beginning of March, is the 

 most favorable time for this operation. The process by slips is 

 very similar to the other ; it is merely cutting off a branch and 

 planting it, differing from the layer, by being separated from its 

 parent before it is able to provide for its own wants ; thus re- 

 sembling a child brought up by hand. They should be planted 

 near the surface, in order to facilitate the sprouting of stems. 

 The last method is by scions or grafting, in which a branch is 

 cut off from one plant and placed in an opening made in an- 

 other. This is the best mode of improving the quality of fruit ; 

 without it, our Apple and Pear species would be poor speci- 

 mens in comparison with what they now are ; of course, in a 

 graft, the tree will bear its own species and the graft also. This 



