2. Leaf, 1/2.

3. Staminate flowering branchlet, 1/2.

4. Staminate flower, enlarged.

5. Pistillate flower, enlarged.

6. Fruit, 1.]

+GINKGOACEAE+

+Ginkgo.[C] Maidenhair Tree+

_Ginkgo biloba L._ [_Salisburia adiantifolia Smith_]

HABIT.--A slender tree in youth, with slender, upright branches, becoming broader with age and forming a symmetrical, pyramidal crown; probably 60-80 feet high, with a trunk diameter of 2-4 feet.

LEAVES.--Cl.u.s.tered at the ends of short, spur-like shoots, or scattered alternately on the long terminal branches; simple; 2-5 inches broad; more or less fan-shaped; usually bilobed and irregularly crenate at the upper extremity; thin and leathery; glabrous, pale yellow-green on both sides; petioles long, slender; turning a clear, golden yellow before falling in autumn.

FLOWERS.--May, with the leaves; dioecious; the staminate in short-stalked, pendulous catkins, 1 to 1-1/2 inches long, yellow; the pistillate more or less erect on the shoot, long-stalked, consisting of 2 naked ovules, one of which usually aborts.

FRUIT.--Autumn; a more or less globose drupe, orange-yellow to green, about 1 inch in diameter, consisting of an acrid, foul-smelling pulp inclosing a smooth, whitish, somewhat flattened, almond-flavored nut.

WINTER-BUDS.--Terminal bud about 1/8 inch long, conical, smooth, light chestnut-brown; lateral buds divergent, usually only on rapid-growing shoots.

BARK.--Twigs gray-brown and smooth; thick, ash-gray and somewhat roughened on the trunk, becoming more or less fissured in old age.

WOOD.--Light, soft, weak, close-grained, yellow-white to light red-brown, with thin, lighter colored sapwood.

NOTES.--Origin in dispute, but probably a native of northern China.

Extensively cultivated in China and j.a.pan, where its fruit is esteemed.

Easily propagated from seed. Thrives in deep, well-drained, rich soil.

Practically free from insect and fungous attacks, and little harmed by the smoke of cities. Probably hardy throughout the southern half of the Lower Peninsula.

+SUMMER KEY TO THE SPECIES OF PINUS+

a. Leaves 5 in a cl.u.s.ter; cones 4-10 inches long. _P.

strobus_, p. 7.

aa. Leaves 2 in a cl.u.s.ter; cones less than 4 inches long.

b. Leaves 1-3 inches long.

c. Leaves about 1 inch long, divergent; cones sessile, pointing forward towards the tip of the branch, persistent 10-15 years, opening very unevenly. _P. banksiana_, p. 9.

cc. Leaves 1-1/2-3 inches long, slightly divergent; cones stout-stalked, pointing away from the tip of the branch, maturing in second season, opening evenly. _P. sylvestris_, p.

13.

bb. Leaves 3-6 inches long.

c. Bark of trunk red-brown; cones maturing in second season, about 2 inches long; cone-scales thickened at the apex, but unarmed. _P. resinosa_, p. 15.

cc. Bark of trunk gray to nearly black; cones maturing in first season, 2-3 inches long; cone-scales thickened at the apex and topped with a short spine. _P. laricio austriaca_, p.

11.

+WINTER KEY TO THE SPECIES OF PINUS+

a. Leaves 5 in a cl.u.s.ter; cones 4-10 inches long. _P. strobus_, p. 7.

aa. Leaves 2 in a cl.u.s.ter; cones less than 4 inches long.

b. Leaves 1-3 inches long.

c. Leaves about 1 inch long, divergent; cones sessile, pointing forward towards the tip of the branch, persistent 10-15 years, opening very unevenly. _P. banksiana_, p. 9.

cc. Leaves 1-1/2-3 inches long, slightly divergent; cones stout-stalked, pointing away from the tip of the branch, maturing in second season, opening evenly. _P. sylvestris_, p.

13.

bb. Leaves 3-6 inches long.

c. Bark of trunk red-brown; cones maturing in second season, about 2 inches long; cone-scales thickened at the apex, but unarmed. _P. resinosa_, p. 15.

cc. Bark of trunk gray to nearly black; cones maturing in first season, 2-3 inches long; cone-scales thickened at the apex and topped with a short spine. _P. laricio austriaca_, p.

11.

[Ill.u.s.tration: +White Pine+

1. Cl.u.s.ter of leaves, 1.

2. Cross-sections of leaves, enlarged.

3. Partly opened cone, 3/4.

4. Cone-scale with seeds, 1.]

+PINACEAE+

+White Pine+

_Pinus strobus L._

HABIT.--A large tree 60-80 feet high, with a trunk diameter of 2-4 feet; forming a wide, pyramidal crown. Formerly trees 100-150 feet in height and 5-7 feet in trunk diameter were not exceptional.

LEAVES.--In cl.u.s.ters of five; 3-5 inches long; slender, straight, needle-shaped, 3-sided, mucronate; pale blue-green. Persistent about 2 years.

FLOWERS.--June; monoecious; the staminate oval, light brown, about 1/3 inch long, surrounded by 6-8 involucral bracts; the pistillate cylindrical, about 1/4 inch long, pinkish purple, long-stalked.

FRUIT.--Autumn of second season, falling during the winter and succeeding spring; pendent, short-stalked, narrow-cylindrical, often curved, greenish cones, 4-10 inches long; scales rather loose, slightly thickened at the apex; seeds red-brown, 1/4 inch long, with wings 1 inch long.

WINTER-BUDS.--Oblong-ovoid, sharp-pointed, yellow-brown, 1/4-1/2 inch long.