[AS. Bot. name Papulus tremula.]A species of poplar tree growing in Europe and in Siberia. It has received the specific name tremula, from the trembling of its leaves, which move with the slightest impulse of the air. The wood is white, soft, light, and smooth. It is not good for fuel, but is much in use for the turning-lathe, in making troughs, trays, and pails. The bark contains a bitter, alkaloid called salicin, and charcoal made from the aspen tree can be used in the manufacture of gunpowder.