52 



Eni)lioi-))ia: Not only all of the fourteen species reported from Indi- 

 ana, but all of the hundred of more species occurring in the United 

 States. 



Rhus Vernix L. Poison Elder. Poison Ash. Poison Dogwood. 



Rhus radicans L. Poison Ivy. Poismi Oak. 



Dirca palustris L. Leather-wood. Moose-wood. 



Aralia spinosa L. Angelica Tree. Hercules Club. 



Solanum Dulcamara L. Poison Nightshade. 



Datura Stramonium L. Jamestown or Jimson-weed. Thorn Apple. 



Datura Tatula L. I'urple-stemmed Jimson. 



Verbascum Thapsus L. Common Mullein. 



Catalpa Catalpa (L.) Karst. Catalpa. Indian Bean. 



Lobelia inflata L. Indian Tobacco. 



Xanthium strumarium L. Cocklebur. Burthistle. 



Solidago: All species to be regarded with suspicion by persons with 

 sensitive skins. Solidago odora Ait., said to be particularly dangerous 

 because of a "volatile oil that is an irritant and rubefacient." 



Leptilon Canadense (L.) Britton. Horse-weed. Flea Bane. 



Bidens frondosa L. Common Beggarticks. Spanish Needles. 



Anthemis Cotula L. Common Dog-fennel. 



Arctium Lappa L. Burdock. 



To these may be added the commonly cultivated— 



Tropa^olum majus L. Nasturtium. 



Nerium Oleander L. Oleander. 



Primula obconica Hance. Primrose. 



This is a rather startling array of dangerous plants, esi)ecially to the 

 field botanist who has been handling most of them with perfect impimity 

 for years. It occurred to me some years ago that it would be interesting 

 to examine the list carefully and so far as possible to conduct a series of 

 experiments confirming or disproving the correctness of the inclusion of 

 the above forms in the list. This I have beeu able to do with the aid of 

 a number of students who offered themselves as subjects for the experi- 

 ments. In the last five years I have licen able to secure twenty-two 

 persons to aid me in the work. 



The most ciu'sory examination bi'caks the preceding list into two 

 sharply separate groups. In the one the skin irritation is due to the action 

 of some specific substance of the plant, as in the case of Rhus; in the 



