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To the Editor.—
It is interesting to note the long history of the existence of poisonous plants. From central Oregon, we have acquired an example of poison sumac (Figure). This specimen is dated from the late oligocene of the tertiary period, more than 35 000 000 years ago. It came from the John Day deposits of volcanic ash. This ash includes many fossils. The poison sumac was identified by expert paleobotanists as Rhus merritti chaneii, a member of the famed Anacardaceae family. The leaf structure is still excellent in these fossilized remains. The climate of the oligocene period was mild, and plant growth was widespread.
Goldman L. The Antiquity of Poisonous Sumac. Arch Dermatol. 1987;123(1):27. doi:10.1001/archderm.1987.01660250031009