The source may not be an unusual plant. In extreme weather, many kinds of plants will "sweat off" hydrocarbons from their leaves. Some of it is a byproduct of the formation of protective waxes on the leaf surfaces.
I live in the forested valley of the Fraser River. Under calm conditions and temperatures well above 35C (in the sun, not shade air temp), you can smell the forest, trapped in the valley. Apparently, hydrocarbons such as turpines are evaporated at great rates. Whether these things assist in heat tolerance or not, I do not know.