POISON SUMAC 405 



is soluble in alcohol and called it toxicodendrol. Schwalbe, on 

 the other hand, states that the poisonous substance is of a volatile 

 nature, being formed in the laticiferous vessels and by osmosis 

 is transferred to the hairs. The poison may be transmitted either 

 by direct contact with the hairs, much as in the same manner with 

 the nettles, or by volatilization of the oil when the hairs are broken. 

 The experience of most plant collectors would seem to indicate 

 that in Poison Ivy there is a volatile toxic constituent. On the 

 other hand, Rost and Gilg were unable to find a volatile poison in 

 either the hairs or pollen of Poison Ivy. In some experiments con- 

 ducted by Warren on pollen grains, similar negative results were 

 obtained. The poisonous principle occurring in several species of 

 Rhus is an amber-red, non-volatile liquid. It is of a resinous nature 

 combining with the alkali hydroxides to form nigrescent compounds 

 and otherwise behaves like certain phenolic derivatives. The 

 toxic resin exists in the plant in the form of an emulsion, which readily 

 blackens with the alkali hydroxides. So delicate is this reaction, 

 that minute amounts of the substance may be detected by means 

 of the microscope, if the plant tissues are mounted in an alcoholic 

 solution of potassium hydroxide. 



RHUS VERNIX. Poison Sumac, Poison Elder or Poison Dog- 

 wood. The plant is poisonous, like Rhus Toxicodendron, and prob- 

 ably contains the same principles. It is a shrub or small tree, found 

 in swamps in the United States and Canada. The leaves are 7- to 

 13-foliate, with obovate or oval, acuminate, entire leaflets; the flowers 

 are small, green, and in axillary panicles; the fruit resembles that 

 of Rhus Toxicodendron. 



Allied Plants. Other species of Rhus are also poisonous, as 

 the western Poison Oak (R. diversiloba) of the Pacific Coast, and 

 the Japanese Lacquer or Varnish tree (R. vernicifera and R. suc- 

 cedanea). The lacquer trees grow wild in both China and Japan, 

 where they are also cultivated. The lac is obtained by incising the 

 bark, and removing it with a pointed spatula. The grayish-white 

 emulsion is strained and on exposure to air it changes to brown, becom- 

 ing finally black. This change is due to the oxidizing enzyme, 

 laccase. The natural lac (Kiurushi) contains a non-volatile, poi- 

 sonous, resin-like principle and is closely associated with other 

 resinous substances. When Japanese lac is thinned with camphor, 

 or mixed with linseed oil, on drying in a moist atmosphere, it forms 

 the most indestructible varnish known. Various pigments are used, 

 as vermilion, gamboge, acetate of iron and other substances. The 

 best glossy black colors are obtained by the addition of iron. 



