rjO ANAC'AUDIACE.E. 



TliiH pommon and, by many people, nmch-droatlod plant opeurs in two 

 rather (liHtinct lornis, which were formerly coiisiilereil sep.irate species, 

 but are now rceojjjiiized as Hpecitically identical, their ditterenceH beii^' duo 

 entirely to the circuniHtances of their growth. A plant growing in an open 

 Hpace with no convenient support near has the habit of a low Hhrub ; while 

 one rooted at the base of a tree or beside u rock puts forth innumerable 

 adventitious rootlets, and 1,'y means of these climbs u^jward vigorously, 

 never stopping, under favorable cireumshuices, until it has reached the 

 highest point attainable. Another curious feature in the growth of the 

 plant as a clindjer is that the increase in the thickness of the stem takes 

 place almost entirely upon the side next the sui)port, whether this be a 

 rock, tree, or any other ol'ject, so that the pith is eccentric. As the root- 

 lets bring no nourishment to the stem, and as they are put forth in <|uantity 

 only when there is something near to lix themselves to, it ap2)ears jjrobable, 

 as the author endeavcn'ed to show some ye.'irs ago, that they are i)roduced 

 by the mere stimulation of contact ; and also that the increased growth 

 Ij on the side of the stem next the support is induced in the same mannei-. 



The climbing plant was formerly denominated 11. i-aiUcans, a name, of 

 course, now discarded. 



Iluhilat. — Common everywhere from Canada to the Gulf of Mexico and 

 westward. 



Rhus venenata Dc CandoUe. — Poison Sumac, Poison Elder. 



l)(:<(rii)tion. — A vigorous shrub, G to 18 feet high, with sniooth, pale 

 gray bark. Leaflets in 3 tob G pairs, with an odd terminal one, obovate- 

 oblong, entire, r-uiicles larger than in the preceding species ; fruit also 

 larger, greenish-yellow or greeni.sh-white. 



Habitat. — Conimon in swamps and wet places fi'om Canada to Floi'ida 

 and westward. 



Tart Used. — The fresh leaves of Rhus Toxicodendron — United. Slates 

 Pharmaeopa)ia. The leaves of It. venenata possess similar properties. 



Constituents. — Tlieso species of rims, together with li. diccrsiloba Tor- 

 rey and G ->* the Pacific Coast and II. pumila Michaux of the Southern 

 States, r the poisonous members of the genus indigenous to North 



Am'' . cir poisonous properties, though dittering in degree, are es- 



sei .vtentical in quality. 11. pamda is said to be the most poisonous 



of tilt; group, while /'. venenata occupies a second place, being itself con- 

 siderably more violent in action than 11. toxicodenaron or It. diversilolm ; 

 the two last-named resendjling each other very much both in habit of 

 growth and in their efleots. The poisonous constituent of these plant.s, 

 though considerably investigated, has not been as yet thoroughly charac- 

 terized. That it is volatile is well known, and that it is an acid principle 

 has also been demonstrated ; but beyond this nothing is definitely known. 

 Though volatile and capable of producing its peculiar etTects upon verj' 

 suscej^tible individuals, even at some distance from the growing plants, it 



