506 WOODY PLANTS OF MASSACHUSETTS. 
be procured from it. To this end, Dr. Bigelow made, in 1815, 
several experiments, which seem to establish this point in a 
manner very satisfactory. 
“A quantity of the juice was boiled alone, until nearly all the 
volatile oil had escaped, and the remainder was reduced almost 
to the state of a resin. In this state, it was applied while warm 
to several substances, which, after cooling, exhibited the most 
brilliant, glossy, jet black surface. The coating appeared very 
durable and firm, and was not affected by moisture. It was 
elastic and perfectly opaque, and seemed calculated to answer 
the purposes of both paint and varnish.””—Med. Bot., I, 101-2. 
The poisonous property, as in most cases of vegetable poisons, 
seems to be removed by evaporation or boiling; and the dry 
varnish would probably be mmnocuous. 
Sp. 5. Tue Poison Ivy. &. toxicodéndron.  L. 
Figured in Bigelow’s Medical Botany, III, Plate 42. 
R. toxicodéndron and radicans of Linneus and other au- 
thors. When climbing over rocks or on the trunks of trees, it 
seems to have been considered FR. radicans ; when standing by 
itself, and forced to erect a portion of its stem, £. toxicodendron. 
I have never been able to find a precise distinction between the 
several forms of this plant, which pass into each other, and am 
glad to see that they are considered by Torrey and Gray as 
only varieties. 
The Poison Ivy is a hardy plant, frequent in moist or shady 
places, chmbing over rocks to which it attaches itself by numer- 
ous radicles which penetrate the investing lchens, or over 
bushes and along the trunks of trees, often to a great height, 
fastening itself to the bark so firmly that it breaks more readily 
than it is detached, and so closely as to impede the growth of 
the plant. 
The leaves are in threes, on a petiole sometimes perfectly 
smooth, sometimes downy, flattened above. The leaflets are 
smooth and shining on both surfaces, broad-ovate, acuminate, 
entire or variously and irregularly toothed and lobed; the lateral 
ones nearly sessile, broader below, the terminal on a stalk six to 
eighteen lines long, or sometimes closely sessile. The sterile 
