BY SUBDIVISION. 193 



cient to occasion a small accumulation, and the shoot- 

 ing out of several germs of roots. 



There are some creeping plants which propagate them- 

 selves in this manner without the aid of man. Their low- 

 er branches, trailing upon the ground, are often partially 

 covered with earth washed over them by the rain : if, in 

 this operation, they are slightly wounded by friction, or 

 the contact of any hard substance, such as gravel or peb- 

 bles, the free passage of the cambium is interrupted, 

 roots strike out, and the branch which connected them 

 with the parent-stock, being in a great measure deprived 

 of its nourishment by the young roots, rots and perishes; 

 the separation is thus made, and the requisite organs being 

 developed, the layer becomes a new individual plant. 



Caroline. I have seen carnations and ranunculuses 

 thus propagated ; and I am delighted to hear the explan- 

 ation of an operation I have often witnessed without un- 

 derstanding it. 



Mrs. B. Laurels and most evergreens are also propa- 

 gated by layers ; and it is the regular mode used in vine- 

 yards. A branch of vine is laid under ground, and the 

 extremity of it raised up above the soil in that spot where 

 you wish to produce 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 ground, as often as it is inten- 

 ded that new roots and stems should shoot 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 par- 

 ticularly suited to the raspberry and every species of bram- 

 ble. 



Caroline. I have heard that there is a tree in Senegal 

 called the Mangrove, or Rhizophora, whose branches, 

 descending to the ground, bury their extremities in the 

 soil, and strike root, thus forming beautiful natural ar- 

 cades around the parent stem. 



1057. What is the result 1 ? 1058. Without the aid of man 

 what plants propagate themselves in this way 1 ? 1059. How is it done! 



1060. How are laurels, evergreens, and vines propagated? 1061. 



What is called the serpentine layerl 1062. In what other way are 

 layers sometimes made 1 ? 



17 



