32 MINNESOTA BOTANICAL STUDIES. 



YI. ON THE POISONOUS INFLUENCE OF 

 CYPEIPEDIIIM SPECTABILE AND 

 CYPEIPEDIU3I PUBESCENS. ' 



D. T. MacDougal. 



The plants which are poisonous to the skin, in a more or less 

 degree, include a large number, many of which are common 

 and well known species. In this connection reference is had 

 only to those plants which, during some stage of their exist- 

 ence, will produce poisoning by contact, or by means of a 

 volatile principle, which acts upon the skin of any person ap- 

 proaching them, and is exclusive of those which are injurious 

 either in the form of extracts or preparations, or in their 

 lengthened application, or in their manipulation in the manu- 

 factures. 



Without doubt the larger percentage of the common plants 

 known to be poisonous, is due to the fact that they offer much 

 more numerous opportunities for observation than do the rarer 

 forms. For it is by no means to be understood, that there are 

 many plants which are always and invariably poisonous. So 

 far as can be learned there are no plants, except perhaps the 

 urticaceous forms, which are injurious to every one handling 

 them. Probably the most virulent of the class of plants refer- 

 red to, are the species of Rhus: yet many persons can handle 

 them without danger at all times, and others are only injured 

 b}^ plants in a certain stage of growth. On the other hand, 

 many of the plants in this category are injurious only to a very 

 small percentage of the persons touching them, so that their 

 irritating qualities might remain undiscovered altogether un- 

 less tested by a large number. As an example, it may be cited 

 that the hop plant, in the limited handling it receives in the 

 domestic garden, is ordinarily regarded as innocuous; yet in 

 extensive hop gardens of California, among the thousands of 

 pickers in the fields, are many who are severely irritated by it. 



1. A preliminary notice was read before the Indiana Academy of Scientie, De- 

 cember. 1893. 



