KEl'ORl 01-' THE BOTAMST 269 



SESSIONAL PAPER No. 16 



Specimens of any suspected herb, shrub, tree or other vegetation or part thereof 

 should be sent whenever practicable. The specimens may be packed between lasers of 

 paper and be sent under cardboard or other protective covering. Any further parti- 

 culars giving a description of the grounds on which the animals have been grazing 

 previous to death will be useful. Indicate whether the animals had access to ditches, 

 ponds, river banks or whether the grounds were stony, dry or wet, etc. 



AH specimens should be addressed to the Veterinary Director General, Ottawa, 

 and should contain, in order to be identified, the name and address of the sender. 

 Specimens not exceeding five pounds in weight, after being securely packed to prevent 

 leakage, are carried free by mail. Specimens over five pounds in weight should be 

 sent by express. 



Investigations of this kind involve considerable trouble both for the investigator 

 and for the collector of material. It is hoped that farmers will go to the trouble of 

 forwarding specimens of plants and stomachs of animals whenever opportunities occur. 

 Tins work is done entirely for their benefit and success depends upon co-operation 

 from all quarters. 



POISON IVY (RHUS TOXICODENDRON, L). 



(Fig. 2G.) 



It is safe to say that no poisonous plant in America is better known by name, than 

 poison ivy. One would consequently expect to find it also one of the most gener- 

 ally known at first hand, of all our plants, but it is astonishing how many people con- 

 fess themselves unacquainted with it. Not only townsfolk, but many farmers, and not 

 a few of those who profess to be interested in natural history studies, are unable to 

 recognize it. This being the case, it is not so strange that there are many misconcep- 

 tions abroad as to its nature, and the precautions to be taken against it.. This should 

 not be so, as the plant is so plentiful in nearly every part of North America, and 

 especially in the east, that almost everyone must have had an opportunity at one time 

 or another, of meeting with it; and as the danger incurred by many people in coming 

 in contact with it is so great, its recognition should be a matter of importance to all. 



Poison ivy differs from the majority of poisonous plants in that it does not 

 require to be eaten in order to produce its ill effects. Mere contact with it is sufficient; 

 end indeed many people declare that they are affected even in its presence, though 

 they do not touch it at all. The possibility of ivy poisoning without contact is not 

 admitted though, by those who have studied the nature of the poison to which it- 

 effects are due. This poison has been found to be a non-volatile oil, to which the name 

 ' toxicodendrol ' has been given. All evidence tends to show that it is a mistake to 

 suppose the poisonous principle can be diffused through the air about the plants. The 

 poisonous substance is found in all parts of the plant, and a very little of it reaching the 

 skin is sufficient to set up its painful irritation. Probably many cases of poisoning 

 which appear to be explainable only on the ground of transmission through the air, 

 might be accounted for by the contact of shoes or clothing with the weed, and then 

 with parts of the body which may not have touched it directly. 



It is well known that not all persons are equally susceptible to injury by poi-;on 

 ivy. Some can handle the plant freely without any fear of unpleasant consequences. 

 It would appear also, as if animals were immune, as birds are reported to feed upon 

 the fruit, and my colleague, Mr. Groh, whose observations are very reliable, stated that 

 poison ivy growing along a fence, was kept almost completely eaten down on the one 

 side, where cattle were being pastured. No effects sufficient to attract notice were 

 suffered by any of the animals. (See note next page). 



Poison ivy grows most commonly along the borders of fields and woods, by road- 

 sides, or in open woods; or less frequently it occurs in deep woods where it may 

 become a tall climber supporting itself on the trunks of trees. In the open it is low 



