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-wliite, 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. nibrum, L. Red Maple. A small tree with red or purple 

 twigs. Leaves simple, broadly ovate, palmately o-5-lol)ed 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 autuiim. Flow^ers 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. Flow^ers appearing with the leaves, on 

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

 none. Keys smooth, wings about 1-1 j in. long. In cold w^oods, 

 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 l)ird'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 Em'ope. 



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, 



