1912] The Ottawa Naturalist. 35 



in dry woods and along road-sides all over the country. But 

 perhaps its favorite habitats are the edges of swamps and in 

 damp, shady places. In such situations it grows remarkably 

 large, its leaflets sometimes attaining the size of a man's hand. 

 It is often described in books as a "climbing shrub" or spoken 

 of as a "vine," and sometimes it does clamber over stones or 

 hoist itself a few feet up a tree trunk by means of its rootlets, 

 but in this district at least the shrubby, erect form is much the 

 commonest, and the plant is seldom found climbing. This is 

 an important point, for those unacquainted with the plant on 

 rinding it described as a vine or a climber, naturally fail to 

 identify the low growing erect form as the true poison ivy. 

 Some botanists distinguish the climbing form as a "variety" 

 and give it the cognomen "radicans," but both forms seem to 

 be merely different habits of the same species. 



In a recent book, Sir Ray Lankster notes several unaccount- 

 able cases of severe dermatitis that occurred in England a year 

 or two ago, and which were finallv traced to Rhus Toxicodendron 

 that had been sold by nurserymen, innocently enough no doubt, 

 instead of a kind of Virginia Creeper (Ampelopsis Veitchii) 

 which the Rhus resembles rather closely. Such ignorance of the 

 poison ivy is not, of course, at all surprising in Europe, where 

 the plant is not indigenous; but in this country, if only as a 

 matter of self-protection, everyone should be able to recognize 

 the ominous triple leaf, and it is remarkable to discover how 

 many people are not acquainted with it. I have seen it, when 

 colored red in the late summer, occupying an honored place in 

 a boquet of wild flowers gathered by an unsuspecting camper. 

 It is true that in the fall when the sap is drying up, it is not as 

 dangerous as in the summer when it is lush and green, but it is 

 an exceedingly risky thing to handle at any time. 



The poisonous principle is a fixed oil which is found in all 

 parts of the plant, and persists in the dead leaves and the wood, 

 even after long drying. Minute dust -like particles of the plant 

 carry it, and very slight traces of it on the clothing may cause 

 an attack in those susceptible. The pollen blown by the wind 

 doubtless accounts for those mysterious and not infrequent 

 cases that occur where no actual contact with the plant has 

 taken place. This oil has no apparent effect on animals, and it 

 is even said that the horse, mule and goat eat the leaves with 

 impunity and that birds feed upon the seeds. Like other oils, 

 it is insoluable in water alone, but mav be readilv washed off 

 with soap and water, and is quite soluable in alcohol. From 

 experiments made some years ago by Mr. V. K. Chestnut, of 

 the United States Department of Agriculture, it appears that 

 its effect on the skin is by no means instantaneous, and if washed 



