Aspens, or Abeles, form a distinct group among the poplars. They are usually smaller trees, especially the American species.

*This question is already answered by my friend and jury colleague at Vienna, Cao-Giovaoi Carlo siemoni, who says this poplar is but a form of P. nigra, and that all the plants are males. He adds that it has long been extensively planned in Lombardy. particularly along the river Po. In evidence of its antiquity, he quotes Ovid's reference to it. - Manual?, d' Arte Forestale, Firenze, 1872, p. 13T.

†Darlington's Agr. Botany, 2d Ed., page 332.