RENOVATION OF WOOD. 



finally run together over the wood (Fig. VII. b), and form a 

 coating below which new Hber and alburnum may be generated. 



Fig. VII. — Iteproduction of tissue upon a decorticated space. 



In cuttings, the " callus," which forms at the end placed in the 

 ground, is the cellular horizontal system, preparing for the 

 reception of the perpendicular system, which is to pass down- 

 wards in the form of roots. Many plants will endure extensive' 

 lacerations of their surface, and close up such wounds with 

 great facility. The weU known fact of large inscriptions cut in 

 trees deeper than the bark (which inscriptions were effected by 

 removing very broad spaces of the bark and wood) being 

 covered over in time by new bark and wood, so as to be no 

 longer visible from the outside, sufficiently prove this. In such 

 cases, however, the reparation of the injury takes place chiefly, 

 if not exclusively, by the annual addition of new matter to the 

 lips only of the wound, the effect of which is to reduce its area 

 annually till at last the wound is closed. 



