176 UTILIZATION OP EXUDED PRODUCTS. 



alcohol, ether, and carbon disulphide, but insoluble in water. They 

 burn with a bright or a smoky flame. 



Resins may be classified into (1) true resins, (2) gum-resins, 

 and (3) oleo-resins. The true resins are (a) hard or copaline, as 

 the resins of Vateria inclica (piney), Hopea odorata, Dipterocarpus 

 tuherculatus, Shorea spp., and Canarium benffalense, or (b) soft or 

 elemi, as the exudation of Bosieellia tliurifera. The gum-resins 

 embrace three sub-classes, (a) the emulsive (e.g., gamboge of Gar- 

 cinia Morella and kino of Pterocarpus Marsupium and Butea fron- 

 dosa), (6) the fetid {e.g., asafcetida and the exudations of Gardenia 

 lucida and gummifera), and (c) the fragrant, this last being further 

 sub-divided into two sections, represented respectively by the exu- 

 dations of Balsamodendron (bdellium) and mango, and that of the 

 genus Styra.x (gum benjamin or benzoin). The oleo-resins embrace 

 balsams (e.g., the gurjun " oil " of Dipterocarpus turhinatus, the 

 wood " oil " of D. Imvis and D. zeylanicus, and the copaiba-like 

 balsam of Hardwickia pinnata), natural varnishes- (e.^., the lacquers 

 of Melanorrhcea usitata, Rhus vernicifera, Semecarpus Anacardium 

 and travancorica, Holigarna longifolia), and turpentines and tars 

 (the products of numerous conifers). 



Gums are found in exploitable quantity only in the bark, while 

 resins are formed in the wood as well as in the bark. In the bark 

 the resin always occurs in special receptacles (resin cells or ducts) ; 

 in the wood there may be special reservoirs, as in pines, or the resin 

 may be secreted in the vessels themselves, as in the wood of the 

 Dipterocarpese. 



According to where the resin or gum is secreted, and to whether 

 the secretion has or has not to be artificially aided, we have three 

 modes of collection, viz., (1) collection of spontaneous exudations, 

 (2) collection from wounds made in the bark, and (3) collection 

 by tapping the wood. 



Article 1. — Collection of spontaneous exudations. 



During the season of rest, especially when the bark becomes dry 

 and cracks, and the tree, unable to transpire, is full of moisture, the 

 low vitality of the numerous cells in the bark results in the forma- 

 tion of gum. It is also at this time that the outflow of resin is most 

 active. The quantity of resin that bursts, through the bark and 

 exudes spontaneously is too insignificant to become an object of re- 

 gular exploitation, and hence only gums are thus collected. Gums 

 obtained in this manner comprise those furnished by Anogeissus lati- 



