11. =Salix rostrata, Richards.= (BEAKED WILLOW.) Leaves oblong to obovate-lanceolate, acute, usually obscurely toothed, sometimes crenate or serrate, downy above, prominently veined, soft-hairy and somewhat glaucous beneath. Twigs downy. Catkins appearing with the leaves.

Fruit-capsules tapering to a long slender beak, pedicels long and slender. A small, tree-shaped shrub, 4 to 15 ft. high, common in both moist and dry ground. New England, west and north.

[Ill.u.s.tration: S. discolor.]

12. =Salix discolor, Muhl.= (GLAUCOUS OR BOG WILLOW.) Leaves lanceolate or ovate-lanceolate, acute, remotely serrate at the base, finely serrate along the middle, and almost entire near the tip; smooth and bright green above, soon smooth and somewhat glaucous beneath; stipules, on the vigorous shoots, equaling the petiole, more frequently small and inconspicuous. Catkins sessile, 1 in. long, appearing before the leaves in the spring; scales dark red or brown, becoming black, covered with long glossy hairs. Fruit in catkins, 2 in. long, the capsules very hairy, with short but distinct style. A very variable species, common in low meadows and on river-banks; usually a shrub, but occasionally 15 ft.

high.

[Ill.u.s.tration: S. cinerea.]

13. =Salix cinerea, L.= (GRAY OR ASH-COLORED WILLOW.) Leaves obovate-lanceolate, entire to serrate; glaucous-downy and reticulated with veins beneath; stipules half heart-shaped, serrate. Flowers yellow; ovary silky, on a stalk half as long as the bracts. A shrub to middle-sized tree, 10 to 30 ft. high, with an erect trunk; occasionally cultivated; from Europe.

[Ill.u.s.tration: S. longiflia.]

14. =Salix longiflia=, Muhl. (LONG-LEAVED WILLOW.) Leaves linear-lanceolate, very long, tapering at each end, nearly sessile, remotely notched with projecting teeth, clothed with gray hairs when young; stipules small, lanceolate, toothed. Branches brittle at base. A shrub or small tree, 2 to 20 ft. high, common, especially westward, along river-banks.

GENUS =92. PoPULUS.=

Trees with alternate, deciduous, broad-based leaves. Flowers in long and drooping catkins, appearing before the leaves are expanded in the spring. Fruit small, dry pods in catkins, having seeds, coated with cottony down, which early in the season escape and float in the wind. On this account the trees are called Cottonwoods in the West. Trees with light-colored, rather soft wood.

* Leaves always white-hairy underneath; more or less deeply lobed; buds not gummy 1.

* Leaves smooth beneath, at least when old. (=A.=)

=A.= Leafstalk decidedly flattened laterally. (=B.=)

=B.= Buds not covered with sticky gum. (=C.=)

=C.= Leaves roundish heart-shaped; bark on trunk greenish-white, 2.

=C.= Leaves large, ovate, with large, irregular, sinuate teeth, 3.

=B.= Buds covered with aromatic, glutinous resin. (=D.=)

=D.= Tree tall, spire-shaped, 5.

=D.= Not very spire-shaped; young twigs sharply angled or winged, leaves 6 to 10 in. long, broadly deltoid, serrate with incurved teeth, 6.

=D.= Not spire-shaped; young twigs not angular, 7.

=A.= Leafstalk not decidedly flattened; leaf-margin crenate.

(=E.=)

=E.= Buds not glutinous; leaves white-woolly beneath when young, 4.

=E.= Buds very glutinous; leaves large, shining green on both sides, 8.

[Ill.u.s.tration: P. alba.]

1. =Populus alba=, L. (WHITE POPLAR OR ABELE TREE.) Leaves roundish, slightly heart-shaped, wavy toothed or lobed, soon green above, very white-cottony beneath even when old; buds without the sticky coating common in the genus. Branches very white with down when young. Root creeping and producing numerous suckers. A large tree, 50 to 80 ft.

high, of rapid growth, often cultivated; from Europe. Leaves and branches very variable, forming several named varieties in the catalogues of the nurseries.

[Ill.u.s.tration: P. tremulodes.]

2. =Populus tremulodes=, Michx. (QUAKING-ASP. AMERICAN ASPEN.) Leaves roundish heart-shaped, with a short sharp point, and small, quite regular teeth; downy when young, but soon smooth on both sides; margins downy. Leafstalk long, slender, compressed, causing the leaves to tremble continually in the slightest breeze. Leaf with 2 glands at the base on the upper surface; buds varnished. A medium-sized tree, 30 to 60 ft. high; bark greenish-white outside, yellow within, quite brittle.

Common both in forests and in cultivation.

[Ill.u.s.tration: P. grandidentata.]

3. =Populus grandidentata=, Michx. (LARGE-TOOTHED ASPEN.) Leaves large, 3 to 5 in. long, roundish-ovate, with large, irregular, sinuate teeth; and when young densely covered with white, silky wool, but soon becoming smooth on both sides; leaf, when young, reddish-yellow; petiole compressed. A large tree, 60 to 80 ft. high, with rather smoothish gray bark. Woods; common northward, rare southward, except in the Alleghanies. Wood soft and extensively used for paper-making.

[Ill.u.s.tration: P. heterophlla.]

4. =Populus heterophlla=, L. (DOWNY-LEAVED POPLAR.) Leaves heart-shaped or roundish-ovate with small, obtuse, incurved teeth; white-woolly when young, but soon becoming smooth on both sides except on the veins beneath. Leafstalk slightly compressed. Shoots round, tomentose. Buds not glutinous. A large tree, 70 to 80 ft. high, not very common; found from western New England to Illinois, and southward.

[Ill.u.s.tration: P. dilatata.]

5. =Populus dilatata=, L. (LOMBARDY POPLAR.) Leaves deltoid, wider than long, crenulated all round, both sides smooth from the first; leafstalk compressed; buds glutinous. A tall tree, 80 to 120 ft. high; spire-like, of rapid growth, with all the branches erect; the trunk twisted and deeply furrowed. Frequently planted a century ago, but now quite rare in the eastern United States. From Europe. It is thought to be a variety of Populus nigra (No. 7).

[Ill.u.s.tration: P. monilifera.]

6. =Populus monilifera=, Ait. (COTTONWOOD. CAROLINA POPLAR.

NECKLACE-POPLAR.) Leaves large, broadly heart-shaped or deltoid, serrate with cartilaginous, incurved, slightly hairy teeth. The rapid-growing young twigs very angular and bearing very large (6 to 9 in. long) leaves. A very large (80 to 100 ft. high) tree, common in the Mississippi valley, but found in western New England and often planted.

[Ill.u.s.tration: P. ngra.]

7. =Populus ngra=, L. (BLACK POPLAR.) Leaves rather large, deltoid, pointed, serrate with glandular teeth, smooth on both sides even when young. Leafstalk somewhat compressed. Buds very sticky. A very variable, large (50 to 80 ft. high), rapidly growing tree with spreading branches.

Occasionally planted. From Europe.

[Ill.u.s.tration: P. balsamifera.]

8. =Populus balsamifera=, L. (BALSAM-POPLAR. TACAMAHAC. BALM OF GILEAD.) Leaves very large, ovate, gradually ac.u.minate, sometimes heart-shaped, finely serrate, smooth, bright green and shining on both sides; leafstalk nearly round; leaves in spring rich yellow. Branches ridged below the leaves; buds large and covered with very fragrant resin. A medium-sized tree, 40 to 70 ft. high, pyramidal in form. Wild in the North and often cultivated.

Var. _candicans_, or Balm of Gilead, has larger and more or less heart-shaped leaves (the larger figure in the cut).

CLa.s.s II. GYMNOSPeRMae.

Plants in which the pistil is represented by an open scale instead of a body with a closed ovary, as in Cla.s.s I.

ORDER =XLI. CONiFERae.= (PINE FAMILY.)

As far as the number of species is concerned, this is the largest order of trees and shrubs of temperate and cold-temperate regions. The order is of the greatest importance, both on account of the valuable timber it furnishes and for its resinous secretions, turpentine and resin.

GENUS =93. PNUS.= (THE PINES.)