THE EESINS. 255 



bitter. It is complex in structure, having no less than 

 three resinous components. It is used in varnishes to give 

 hardness and gloss. It is also employed in medicine. 

 From an Australian species (C Preissii) a nearly related 

 product called Pine Gum is obtained. 



223. From another Coniferous tree {Dammara orientalis), 

 the important resin Damar is obtained. The family to 

 which this large tree belongs is the Coniferce. It grows in 

 the Moluccas, Borneo, Java, Sumatra, etc. Much of the 

 resin exudes spontaneously. The trees are also cut low 

 down to the ground, and the resin collects in reservoirs. 

 In the mountainous regions of Sumatra the resin masses 

 fall into the streams, and thus are washed down. Damar 

 is colorless or yellow, and sometimes cloudy. The fresh 

 surface is vitreous. It becomes sticky in the hand. It has 

 a balsamic odor; it varies in weight, having a specific 

 gravity from 1.04-1.12. Like the preceding, Damar is 

 also very complex, having among its constituents several 

 resinous bodies, a trace of gum, and a very small quantity 

 of mineral substance. It furnishes a very clear varnish, 

 and is often used in mounting objects for the microscope. 



224. Gum-Lac forms a resinous crust on the twigs and 

 branches of various trees in India. The largest amount is 

 from Croton lacdfera, a plant of the Spurge family (Eu- 

 phorbiacece). The exudation is caused by myriads of insects 

 (^Coccus laccce), allied to the cochineal insect. The females 

 collect on the young and soft twigs and insert their long 

 proboscis into the cortex to obtain nutriment from the 

 plant. They then exude a resinous secretion from their 

 entire bodies, and become enclosed in a continuous crust of 

 resin. The twigs loose their leaves and die ; in the mean- 

 time twenty or thirty larvse develop, escape through the 



