The English aspen (P. tremula) considerably resembles our native aspen; but the buds are somewhat gummy. The Athenian poplar (P. Gr�ca) is a tree about 40 feet high, with smaller, more rounded, and equally serrated foliage. The common Black European poplar (P. nigra) is also a large, rapidly growing tree, with pale-green leaves slightly notched: the buds expand later than most other poplars, and the young leaves are at first somewhat reddish in color. The Necklace-bearing poplar (P. monilifera), so called from the circumstance of the catkins being arranged somewhat like beads in a necklace, is supposed to have been derived from Canada, but there are some doubts respecting its origin: in the south it is generally called the Virginia poplar.
