320 



BOTANY AND PHARMACOGNOSY. 



spatula. The grayish-white emulsion is strained and on exposure 

 to air it changes to brown becoming finally black. This change 



Fig. 163. A, pinnately compound leaf of poison sumac (Rhus vemix); B, flowering 

 branch, and C, fruiting branch of the same; D, tri-foliate leaves of poison ivy (.Rhus radicans) ; 

 E, fruiting branch of the same with axillary cluster of globular drupes. 



is due to the oxidizing enzyme laccase. The natural lac (Ki- 

 urushi) contains a non-volatile poisonous principle, resembling 



