Definitions for gas plant
Random House Webster's College Dictionary
a plant, Dictamnus albus, of the rue family, native to Eurasia, having clusters of flowers and strong-smelling foliage that emits a flammable vapor.
Ref: Also called fraxinella , dittany.
fraxinella, dittany, burning bush, gas plant, Dictamnus alba(noun)
Eurasian perennial herb with white flowers that emit flammable vapor in hot weather