XXV. POISONOUS INFLUENCE OF YAEIOUS SPE- 

 CIES OF CYPRIPEDIUM. 



D. T. MacDougal. 



In a brief note published in a previous number of this bulletin 

 (Part I. p. 32. 1894.) the writer detailed the results of some 

 observations tending to show that the leaves and stems of adult 

 plants of Cypripedium spectabile and C. pubescens exert a pois- 

 onous influence on the human skin. The experiments from 

 which this conclusion was derived were performed in the open 

 air, in the localities in which the plants grew. Although no 

 specimens of Rhus or other poisonous plant were known to 

 occur within a mile of the scene of the experiments, it was 

 determined that they should be repeated under circumstances 

 in which evexy possible source of error should be eliminated. 

 In order to accomplish this, a number of root-clumps of C. 

 spectabile, C. pubescens and C. parviflorum were procured from 

 a reliable dealer and placed in the plaot houseun der such con- 

 ditions that leafy stems could be obtained during a period from 

 February 1, to May 10, 1894. During the earlier part of this 

 time the temperature of the outside air was such as to preclude 

 any interference from plants growing in a state of nature, and 

 the plant house contained no known poisonous plants. Careful 

 tests were made with C. spectabile on nine persons, six of whom 

 were poisoned in a degree corresponding to the manner of 

 application of the plants to the skin. A similar percentage of 

 the students in the department were reported to be susceptible 

 to the action of various species of Rhus. Tests with the stems 

 and leaves of C. pubescens gave about the same results as C. 

 spectabile. Although these tests were a severe drain on the 

 enthusiasm of the subjects they were repeated with C. parvi- 

 florum, which also exhibited a dermatitic action. These tests 

 were also repeated in April, 1895, and the poisonous influence 

 of the three species named may be considered as established 

 beyond all doubt. 



Specimens of the pointed and glandular hairs, which are 

 found in abundance over the entire plant, and were de- 

 scribed in the previous note, were taken from the plant and 

 touched separately to the skin. It was shown that the irritant 

 action was due to the secretion of the glandular hairs only. 

 If the development of the glandular hairs is followed it will be 



