62 



CASHEW FAMILY (AnacardiacecE) 



POISON IVY (Rhus Toxicodendron L.) {Toxicodendron Toxicodendron 



(L.) Brit.) 



Plate XXIV. 



Common Names: — Poison-ivy is also recognized under the names 

 poison-oak, poison-vine and three-leaved ivy. 



Desckiption: — Poison-ivy is a low shrub which is propagated by 

 under-ground branches as well as by seeds. It scrambles over stumps 

 of trees or, as in the case of the variety radicans, it climbs by means of 

 serial rootlets to some height up fence posts and the trunks of trees. The 

 long stalked leaves are divided into three distinct leaflets, which are mostly 

 ovate, pointed, entire or with a few irregular coarse teeth, bright green 

 above, paler and slightly hairy beneath, changing to rich autumnal colours. 

 The flowers are small, inconspicuous, greenish or whitish, loosely clustered 

 in the axils of the leaves. As the flower cluster is surpassed by the long- 

 stalked leaves it is seldom seen unless the foliage is moved aside. The 

 berries are greenish-white or cream coloured, slightly shining, round, 

 smooth, with longitudinal ridges at intervals. The flowers are in bloom 

 from April till June. 



Distribution: — It is a native of Canada and is commonly found in 

 hedgerows, thickets and dry woods from Nova Scotia to British Columbia, 

 where it passes into a thicker-leaved and smoother form {R. Rydbergii 

 Small). 



Poisonous Properties: — Poison ivy is the worst vegetable skin 

 poison in America, hundreds of people being poisoned each year. The 

 poisonous constituents have not yet been satisfactorily determined. 

 Cases of poisoning are often reported where the individual has passed the 

 plant without coming in contact with it. This has been explained by the 

 fact that pollen grains, minute hairs and even exhalations from the plant 

 are sufficient to cause eruptions on the skin of a susceptible person. The 

 poison may even be carried on the clothing or tools of someone who has been 

 in contact with it, or it may be that, as the effect of the poison does not 

 appear for some time, the occasion of coming in contact with it may have 

 been quite forgotten. On the other hand, many people handle it frequently 

 with no ill effect. 



Cattle can eat it with impunity, but dogs are poisoned by it. 



Symptoms: — Inflammation of the skin begins to appear from eighteen 

 hours to several days after contamination, and is characterized by intense 

 irritation and burning, swelling and redness, followed by blisters and pain. 

 Symptoms of internal poisoning are burning thirst, nausea, faintness, 

 delirium, and 'convulsions. 



