THE HAMILTON ASSOCIATION. 1 25 



vicinit}* by numerous thread-like rootlets given off from the stem. 

 Sometimes it climbs spirally to the tops of our tallest trees, attain- 

 ing a height of forty or fifty feet, again it is met with along the sides 

 -of fences which serve as a convenient support, or crawling over bush 

 or rocks, along the ground, in which cases it never exceeds from one 

 to three feet in height. This low form sends off many small branches, 

 the pendulous extremities of which often give the plant a bushy ap- 

 pearance. The stems are from a quarter of an inch to two inches 

 in thickness, and covered with a grayish-brown bark. The leaves, 

 which are said to be eaten by cattle with impunity, are trifoliate ; 

 the leaflets being rhombic-ovate, pointed, pubescent beneath, and 

 variously notched, of a shining red when they first appear in spring, 

 but bright green at maturity. The flowers are small, greenish-white 

 ^ in color, and disposed in simple axillary racemes. The fruit is a 

 round, dry berry, about as large as a pea, of a pale green color, and 

 ripe in October. As in Rhus Venenata, from the bark when 

 wounded exudes an acrid, milky juice, which exposed to the air for 

 a few hours changes to an intense black, which will leave indelible 

 stains on linen or cotton, not effaceable by any known chemical, and 

 which has been used as a marking ink. The researches of Professor 

 Maisch have proved that the acridity of the juice of Rhus Toxico- 

 dendron is due to the presence of a hitherto unknown" volatile acid, 

 analagous to, but distinct from, formic and acetic. Toxicoden- 

 dric acid, when isolated, is found to affect the skin, either by 

 direct contact or by its vapour, exactly as the fresh plant itself does, 

 proving beyond doubt that the poisonous properties of the plant are 

 due to it. This principle is in a great measure dissipated in the 

 process of drying, and hence dried preparations of the plant are 

 much less apt to act noxiously, though even these should be hand- 

 led with great care by such as are susceptible to poisoning by it. 

 The plants for which Rhus Toxicodendron is most often mistaken 

 are the Virginia Creeper or American Ivy {Ampelopsis quinquefolid) 

 with which the climbing variety often entwines itself, and the 

 uralias nudicaulis and quinqnefolia^ commonly known as Wild Sar- 

 saparilla and Ginseng, often found growing with the low form. 

 These plants are very easily distinguished if one will take the trou 

 ble to remember a single simple distinctive mark, viz., that they 

 have ^2^^ leaflets on a single leaf-stalk, whereas the poison ivy has 

 only three. Other distinguishing marks are that the aralias have 



