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