B153 

 (leaf 2) 



ginseng family (Araliaceae). McNair 3 indicates that perhaps the 

 earliest mention of these plants in North America is by the re- 

 doubtable Captain John Smith in 1609, who compared their 

 appearance to that of English ivy (Hedera helix). Poison-ivies 

 and poison-oaks are shrubs or woody vines having leaves composed 

 of three leaflets, which vary from untoothed (entire) to coarsely 

 toothed or wavy-margined or three- to seven-lobed, and turn a bril- 

 liant hue in the fall. The small, greenish, yellowish, or whitish 

 flowers are borne in rather dense clusters (panicles) ; white or ivory- 

 colored, berrylike fruits, (drupes) usually persist on the plant for 

 a considerable period during the fall and early winter. 



The typically eastern common poison-ivy (T. ra'dicans, syn. R. 

 toxiooderi dron ra'dicams), which extends as far west as the eastern 

 edge of the range country, is a woody vine that climbs by means 

 of masses of small aerial rootlets on the stems; it frequently ascends 

 tall trees, sending out branches horizontally in such manner that it 

 is sometimes mistaken for the tree itself. Everything considered, 

 this is probably the most pestiferous plant in the more eastern por- 

 tions of the United States. Grubbing and the use of various chemi- 

 cals (such as common salt, crank-case oil,, kerosene and sodium 

 chlorate) are the usual methods of eradicating poison-ivy, but suc- 

 cess has been obtained in a number of places by allowing goats, sheep, 

 and cattle to graze the plant closely and continuously. 4 5 Sheep 

 and goats are especially efficient in cleaning out areas along walls and 

 fences. 



Pacific poison-oak (T. diversilo'bum, syn. R. diversilo'ba) , which 

 either is a many-stemmed, erect bush or climbs by adventitious root- 

 lets, ranges from Washington to California. The three leaflets are 

 variable, roundish to egg-shaped, and diversely lobed or toothed, 

 occasionally resembling an oak leaf. Jepson rates it as the most 

 widely distributed shrub in California. It is often very abundant 

 and ranges from the coastal foothills to central elevations of the 

 ponderosa pine belt. This species produces a large amount of readily 

 accessible foliage of slight to fair palatability for cattle and sheep 

 and, on many ranges, it is an important secondary browse. McNair 7 

 reports but little apparent variation in the degree of virulence of the 

 poisonous sap of this species throughout the year, and that all parts 

 of the plant are toxic except the anthers and pollen, the true woody 

 tissue (xylem), the cork cells, the epidermis, and the minute hairs 

 (trichomes). 



Poison-sumac (T. ver'nix, syn. R. ver'nix), an erect shrub or small 

 tree common in wet places and lowlands east of the Mississippi 



3 McNair. .T. B. EHUS DERMATITIS FROM EHDS TOXICODENDRON, RADICANS AND DIVER- 



SILOBA (POISON IVY) : ITS PATHOLOGY AND CHEMOTHEEAPY. 298 pp., illUS. Chicago. 



[1923.] 



* Grant, C. V., and Hansen, A. A. POISON IVY AND POISON SUMAC AND THEIE ERADICA- 

 TION. U. S. Dept. Agr. Farmers' Bull. 1166, rev., 14 pp., illus. 1929. 



8 Alexander, A. S. SHEEP KILL POISON IVY. Amer. Sheep Breeder and Wool Grower 

 47 : 324-325. 1927. 



8 Jepson, W. L. A MANUAL OF THE FLOWERING PLANTS OF CALIFORNIA. 1,238 pp., illus. 

 Berkeley, Calif. [1925.] 



7 McNair, J. B. A STUDY OF RHUS DIVERSILOBA WITH SPECIAL REFERENCE TO ITS 

 TOXICITY. Amer. Jour. Bot. 8 : 127-146, illus. 1921. 



