He taught botany and plant taxonomy, and focussed his research on the flora of Pennsylvania, co-authoring the 1979 "Atlas of the Flora of Pennsylvania".
In 1979 Wahl co-authored the 1979 "Atlas of the Flora of Pennsylvania". He taught botany and plant taxonomy, focusing his research on the flora of Pennsylvania.
He taught botany and plant taxonomy, focusing his research on the flora of Pennsylvania. In 1979 Wahl co-authored the 1979 "Atlas of the Flora of Pennsylvania".
He taught botany and plant taxonomy, focusing his research on the flora of Pennsylvania. In 1979 Wahl co-authored the 1979 "Atlas of the Flora of Pennsylvania".