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The genus Rhus contains four species which are recognized as capable of producing toxic symptoms when applied to the skin of susceptible persons. These are Rhus venenata, swamp or poison sumac; Rhus toxicodendron (Rhus radicans), the ordinary poison ivy; Rhus diversaloba, the poison oak of the Pacific slope, closely allied to Rhus toxicodendron; and Rhus vernicifera, the lacquer plant of Japan and China. The first of these, Rhus venenata, is confined to the eastern part of North America; the second, Rhus toxicodendron, is found over large parts of North America. So far as I know, it does not occur in western North America, its place there being taken by Rhus diversaloba. Rhus vernicifera occurs native only in eastern Asia, and with it is said to grow another poisonous species, but whether this is Rhus toxicodendron or Rhus diversaloba I do not know.
The eruptions produced in susceptible persons by all