DICOTYLEDONOUS PLANTS 141 



stipules. Flowers regular, mostly somewhat monoecious or 

 dioecious, in axillary and terminal cymes or racemes. Calyx 

 4-9-parted. Petals as many as the lobes of the calyx or 

 none. Stamens 4-12, hypogynous. Ovary 2-celled ; styles 2. 

 Fruit a double key.* 



ACER, Tourn. 

 Characteristics of the genus as above given for the family. 



1. A. saccharinum, L. (A. dasycarpum, Ehrh.). WHITE MAPLE, 

 RIVER MAPLE. A tall tree with the main branches slender and 

 rather erect. Leaves very deeply 5-lobed, with the notches rather 

 acute, silvery-white, and when young downy on the lower surface, 

 the divisions narrow, coarsely cut and toothed. Flowers greenish, 

 in umbel-like clusters, appearing long before the leaves. Petals 

 absent. Fruit woolly at first, then smooth, with diverging wings, 

 the whole 2-3 in. long. Common on river banks S. and W., also 

 planted for a shade-tree, but not safe, as the branches are easily 

 broken off by the wind. 



2. A. rubrum, L. RED MAPLE. A small tree with red or purple 

 twigs. Leaves simple, broadly ovate, palmately 3-5-lobed or some- 

 times merely serrate or cut-toothed, taper-pointed at the apex, 

 rounded or heart-shaped at the base, smooth or downy, becoming 

 bright red in autumn. Flowers appearing before the leaves on erect, 

 clustered pedicels. Petals red or yellow, oblong or linear. Fruiting 

 pedicels elongated, and drooping. Key red, smooth, wings about an 

 inch long. Swamps and river banks E.* 



3. A. saccharum, Marsh (A. saccharinum, Wang.). SUGAR MAPLE. 

 A large tree. Leaves simple, palmately lobed, truncate or heart- 

 shaped at the base, lobes sinuate-toothed and acuminate, pale and 

 slightly downy beneath. Flowers appearing with the leaves, on 

 clustered drooping pedicels. Calyx bell-shaped, fringed. Petals 

 none. Keys smooth, wings about 1-1^ in. long. In cold woods, 

 more abundant northward. The sap of this tree is the principal 

 source of maple sugar, and some forms of the tree produce the 

 curled maple and bird's-eye maple used in cabinet-making.* 



4. A. Pseudo-Platanus, L. SYCAMORE MAPLE. Easily recognized 

 by its drooping clusters of rather large green flowers, which appear 

 with the leaves. Cultivated from Europe. 



5. A. platanoides, L. NORWAY MAPLE. A large tree, with 

 milky sap, which exudes from broken shoots or leafstalks in the 

 spring. Cultivated from Europe ; a very desirable shade-tree. 



6. A. Negundo, L. Box ELDER. A small tree. Leaves opposite, 



