Deciduous shrubs or trees. Twigs moderate, rounded; pith continuous, pale. Buds moderate, solitary or collaterally multiple, ovoid or conical, sessile or stalked, with 1 or several pairs of exposed scales. Leaf-scars opposite (very exceptionally whorled in some individuals), curved or U-shaped; bundle-traces usually 3, but sometimes 5, 7, or 9, or more numerous; stipule-scars none.
Fig. 194. Acer spicarum.
Fig. 195. Acer pensylvanicum.
Fig. 196. Acer plaranoides.
Fig. 197. Acer saccharum.
Fig. 198. Acer nigrum.
Fig. 199. Acer rubrum.
Fig. 200. Acer saccharinum.
Fig. 201. Acer negundo.
Bud-scales 2, valvate
b. Buds glabrous, thick, blunt, 8-10 mm. long
b. Buds puberulent, short, slender, 5 mm. long
Bud-scales more than 2
b. Buds red, brown, or black; twigs not green
c. Terminal buds usually 5 mm. or more long;sap milky
c. Terminal buds usually less than 5 mm. long; sap clear
d. Buds brown or black; scales 6 or more
e. Twigs glossy-buff or reddish-brown;buds dark, glabrate
e. Twigs dull straw-color, smooth and shiny, with somewhat prominent len-ticels; buds straw-color, hairy
d. Buds reddish or orange;
scales about 4
e. Twigs bright chestnut-brown; inner bark with a rank odor
e. Twigs red and lustrous; inner bark not rank
b. Twigs green; buds covered with a dense white pubescence
1. A. spicatum Lam. Mountain Maple. Shrub or small tree up to 10 m. high, with thin, rather smooth, brown or grayish-brown bark mottled with dingy gray patches; young twigs grayish-pubescent; buds short-stalked, small, about 5 mm. long; terminal buds larger. Cool woods, Newfoundland to Saskatchewan, south to Iowa, Ohio, and the mountains of Georgia and Tennessee (Fig. 194).
2. A. pensylvanicum L. Striped Maple. Moosewood. A small tree up to 10 or 12 m. high, with smooth bark, becoming conspicuously striped with white lines; twigs smooth, thick, green, changing to red; lenticels few; buds stalked, about 1 cm. long, tapering but blunt-pointed, red, glossy, glabrous except for the ciliate margins of the scales; leaf-scars broadly U-shaped, almost encircling the twig. Cool woods, Quebec to Manitoba, south to Michigan, Ohio, and the mountains of Tennessee and Georgia (Fig. 195).
3. A. platanoides L. Norway Maple. Tree to 30 m. high; bark rough, broken; twigs thick, with milky sap; terminal bud plump, large and conspicuous, usually more than 5 mm. long. Introduced from Europe, much planted and sometimes escaping (Fig. 196).
4. A. saccharum Marsh. Sugar Maple. Tree to 40 m. high, with gray, furrowed bark; twigs slender, dull, smooth, reddish-brown to orange-brown; buds brown, conical, sharp-pointed, glabrous or hairy at the apex, the terminal one 5 mm. or less in length; leaf-scars U-shaped or V-shaped, nearly encircling the stem. Rich woods, Quebec to Manitoba, south to Georgia, Mississippi, Arkansas, and Texas (Fig. 197).
5. A. nigrum Michx, f. (A. saccharum var, nigrum (Michx, f.) Britt.). Black Sugar Maple,. Black Maple. A tree 40 m. high, with dark gray bark; twigs slender, glossy, buff; lenticels prominent; buds dark, hairy; leaf-scars U-shaped or V-shaped. Rich woods, Quebec to Minnesota and South Dakota, south to Georgia and Louisiana (Fig. 198).
6. A. rubrum L. Red Maple. Tree up to 40 m. high; bark on young trunks smooth and light gray, on older trunks dark grayish and rough; twigs rather slender, green, becoming glossy red as winter progresses; buds reddish, obtuse, accessory flower buds developing towards spring; flowers red, beginning to bloom in March. Rich soil, Newfoundland to Manitoba, south to Florida and Texas (Fig. 199).
7. A. saccharinum L. Silver Maple. A tree up to 40 m. high; bark on young trunks smooth and light gray, on older trunks brown and shallowly fissured; crushed twigs with a rank unpleasant odor; buds reddish, obtuse, sessile or short-stalked; flower buds spherical, accessory; margin of scales ciliate, often lighter in color; flowers greenish-yellow or reddish, beginning to open in February. River-banks and bottomlands, New Brunswick to Minnesota and South Dakota, south to Florida and Arkansas (Fig. 200).
8. A. negundo L. Box Eider. Tree up to 20 m. high; bark dark gray or brown, divided into broad ridges; twigs moderate, green, smooth, sometimes glaucous, with scattered, rather prominent lenticels; buds sessile or short-stalked, large, ovoid, the terminal acute and the lateral obtuse, covered with gray hairs; leaf-scars V-shaped, encircling the stem so that the adjacent edges of opposite scars meet at a very sharp angle; bundle-traces usually 3. Riverbanks, Florida to Texas, Arizona and Nevada, north to Maine, Manitoba, Saskatchewan, and Alberta (Fig. 201).