POISON IVY. 24 
The size of the stem in this vine is commonly 
not more than an inch. Sometimes, however, in 
very old plants, it is found several times as large; 
It is usually compressed on the side which 
adheres to the support. In favourable situations 
it ascends to the tops of the highest rocks and 
trees, and is often seen restoring to decayed 
trunks the verdure which they have lost. | When 
it does not meet with an elevated prop, the plant 
becomes stunted in its growth, is more branched, 
and affects a spiral mode of growth; or falls to 
the ground, takes root and rises again. Ni 
- The genus Rhus is placed by Linneeus in 
the class Pentandria, and order Trigynia, ‘The 
present species, however, is dicecious, a fact 
which is also true of most of the American 
species of Rhus which I have examined. The 
Rhoes belong to the Linnean natural order 
Dumose, and to the Terebintacew of Jussieu. 
The leayes of the Rhus radicans are ternate, 
and grow on long  semicylindrical petioles. 
Leafets ovate or rhomboidal, acute, smooth and 
shining on both sides, the veins sometimes a 
little hairy beneath. The margin is sometimes 
entire and sometimes. variously toothed and. 
lobed, in the same plant. ‘The flowers are small 
and greenish white. They grow in panicles or 
