126 JOURNAL AND PROCEEDINGS. 



regularly serrate leaves and in nudicaulis the flower-stem is separate 

 from the leaf-bearing one. 



The toxical effects of the poisonous species of Rhus are pro- 

 duced in various ways and degrees of severity, but in all cases they 

 are due to absorption by the system of toxicodendric acid. They 

 may be the result of direct contact with any part of the plant or its- 

 juice ; of exposure to smoke from the burning of it ; of inhaling 

 the steam arising when making pharrnaceutical preparations of it ;. 

 of internal use ; and of emanations from the growing plant. The 

 most specially noteworthy of these methods of poisoning is that by 

 exhalations from the living plant itself. According to Cazin, such 

 exhalations are only given off when the plant is not exposed to the 

 sun's rays (as when it grows in the shade and at night) and consist 

 of hydrocarburetted gas mixed with toxicodendric acid in a volatile 

 state. That they will cause poisoning in those exposed to their 

 influence, without actual contact with the plant, and even at con- 

 siderable distances, is doubted by many scientists, but there is 

 considerable weight of evidence pomting that such is really the case, 

 Wyville Thompson, of the late Challenge exploring expedition, states 

 that among the blacks of the West Indies there is a superstition that 

 ?ome species of Rhus will poison without actual contact. Aborig- 

 inal traditions are rarely found to exist without some foundation, and 

 in this case so strong a one that it should have prevented, the report 

 being called a superstition without fuller investigation. I could cite 

 a number of instances of poisoning, both recorded and coming under 

 my own notice, where all the evidence goes to show that there was 

 no possibiliiy of contact with the plant. "A lady of known suscep- 

 tibility was attacked after being out driving, though she had never 

 left the vehicle, which kept the centre of the road. Here the near- 

 est distance of possible exposure would be that of plants growing, 

 where they were afterwards discovered, along the fence, a distance 

 of over twenty feet." Again, a medical friend of my own experienced 

 a severe attack after passing, at a distance of at least three feet, a 

 thicket in which grew a mass of the plant ; while a gentleman so 

 noted in the scientific world as to vouch for the accuracy of his 

 powers of observation, while engaged in geological researches, found 

 to his cost the effect of passing some, though he had previously 

 noted it, and was hence most scrupulous not to let it touch him. It 

 seems to me, too, that the knowledge of this method of poisoning 



