486 RUBBER 



until the intervening space of bark becomes too narrow or ex- 

 hausted of latex, when the operation may be repeated on a fresh 

 quarter of the stem. The tapping. may thus be extended over 

 almost the whole year. Each following year the opposite or 

 adjacent quarter may be operated upon, the whole area thus occu- 

 pying from 4 to 6 years, by which tirne the renewed bark on the first 



2 3 



TAPPING KNIVES. 



1. Farrier Knife. 2. Barrydo Knife. 3. Baniber's Ceara Pricker. 



quarter should be ready for re-tapping. It is essential to prevent 

 the incision from penetrating the cambium (see under Plant Life), 

 otherwise a knotted condition of the stem will be produced, which 

 will render tapping difficult, and if the cambium be much injured 

 the life of the tree will be affected. 



Coagulation. The latex coagulates on exposure to the air, 

 and that of some species coagulates much more rapidly than 



