The Willow family, which includes also the Poplars, comprises about 200 species, a large proportion of which are distributed in temperate and arctic zones. Several shrubby species extend far into the arctic regions.

On the whole this family is not important commercially, but with the disappearance of the more valuable kinds of trees the rapid-growing and easily-propagated Willows and Poplars are receiving more attention.

The 2 genera belonging to this family are given below:

Salix, (page 51).—This genus comprises no fewer than 175 known species, 100 of which are native to North America. The following species are reported from West Virginia: S. nigra, Marsh., S. amygdaloides, Aud., S. discolor, Muhl., S. humilis, Marsh., S. cericea, Marsh. and S. cordata, Muhl. Doubtless several other species occur in the State. The task of determining the different species of Willows is one for the specialist who has devoted much time to their study. For this reason only one species, the common Black Willow of our stream banks, is described and illustrated in this bulletin. The most common introduced Willows are the well-known Weeping Willow (Salix babylonica, (L.)) and a yellow-twigged variety of the White Willow (Salix alba, var. vitellina, (L.) Koch.).

Populus.—The species of Poplars and Aspens number 27 of which 19 are native to North America and 3 to West Virginia. White Poplar (P. alba, (L.)) and Balm of Gilead (P. candicans, Ait.) are the principal introduced species planted in the State.

KEY TO THE SPECIES OF POPULUS

• Leaves broadly deltoid, acuminate, marginal teeth somewhat incurved; trees of stream banks and extensively planted along streets
• P. deltoides, p. 57.
• Leaves ovate to sub-orbicular.
• Leaves coarsely sinuate-toothed, 3-5 inches long
• P. grandidentata, p. 55.
• Leaves finely serrate, less than 3 inches long
• P. tremuloides, p. 53.