In his "Biblical Researches in Palestine", American biblical scholar Edward Robinson describes it as the fruit of the "Asclepias gigantea" vel "procera", a tree 10–15 feet high, with a grayish cork-like bark called "'osher" by the Arabs. He says the fruit resembled "a large, smooth apple or orange, hanging in clusters of three or four." When pressed "or struck, it explodes with a puff, like a bladder or puff-ball, leaving in the hand only the shreds of the thin rind and a few fibers. It is indeed filled chiefly with air, which gives it the round form; while in the center a small slender pod runs through it which contains a small quantity of fine silk, which the Arabs collect and twist into matches for their guns."