Taxa of Poison Oak, Poison Ivy, and Poison Sumac

Kingdom Plantae
  Subkingdom Viridaeplantae
     Infrakingdom Streptophyta
        Division Tracheophyta
           Class Magnoliopsida
              Superorder Rosanae
                Order Sapindales
                   Genus Toxicodendron 
                      Species pubescens  Atlantic Poison Oak
                      Species diversilobum Pacific Poison Oak
                      Species vernix Poison Sumac
                      Species radicans Poison Ivy
Source: http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=28818                       

Leaves of the poison plants
Source: http://www.webmd.com/skin-problems-and-treatments/poison-ivy-oak-and-sumac-leaves

Useful Links
How to distinguish poison ivy and other poison plants?
http://www.fda.gov/forconsumers/consumerupdates/ucm049342.htm        

Poison Oak in different seasons:
http://www.californiajeeper.com/poison-oak.htm