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SCIENTIFIC AND APPLIED PHARMACOGNOSY 



green and in loose axillary panicles; the fruit is a globular, glabrous, 

 grayish drupe. 



The nature of the poisonous constituents of Poisin Ivy is not 

 definitely known. It was originally considered to be in the nature 



FIG. 173. Rhus Toxicodendron: A, flowering branch showing the characteristic 

 3-foliate, long petiolate leaves, the leaflets in the shrubby, climbing plants, 

 being frequently dentate or lobed. The flowers are small, greenish and 

 arranged in axillary panicles. B, a staminate flower. C, a longitudinal sec- 

 tion through the pistil. D, a fruit which is sub-globular, nearly glabrous or 

 slightly pubescent, the thin epicarp falling away eventually from the granular 

 waxy, multicostate mesocarp. E, transverse section of inner portion of 

 epicotyl; C, cells of cortex; L, leptome in which there is a single large resin 

 canal (R) such as is common to all the Anacardiaceae; M, cambium; //, 

 hadrome in which there are a few spiral tracheae and some young libriform. 



F, surface section of the dorsal or lower epidermis of a leaflet, showing the 

 lateral undulate walls of the epidermal cells and two of the stomata, which 

 lack subsidiary cells, and are raised slightly above the adjoining epidermis. 



G, several of the pointed, non-glandular hairs. H, two of the glandular 

 hairs. After Holm, Merck's Report, 1910, p. 95. 



of a volatile principle. Pfaff and his pupils seemed to show that 

 the poisonous principle was a non-volatile, brownish-red resin which 



