ACERACEJE 625 



appearing with or later than the leaves ; bracts minute, caducous ; calyx 

 colored, generally 5-parted, the lobes imbricated in the bud ; petals usually 

 5, imbricated in the bud, or ; disk annular, fleshy, more or less lobed, with 

 a free margin ; stamens 4-10, usually 7 or 8, inserted on the summit or inside 

 of the disk, hypogynous ; filaments distinct, filiform, commonly exserted in the 

 staminate, shorter and generally abortive in the pistillate flower ; anthers ob- 

 long or linear, attached at the base, introrse, 2-celled, the cells opening longi- 

 tudinally ; ovary 2-lobed, 2-celled, compressed contrary to the dissepiment, 

 wing-margined on the back ; styles 2, inserted between the lobes of the ovary, 

 connate below and divided into 2 linear branches stigmatose on their inner 

 surface ; ovules 2 in each cell, collateral, rarely superposed, ascending, attached 

 by their broad bases to the inner angle of the cell, anatropous or amphitropous ; 

 micropyle inferior. Fruit composed of 2 samaras separable from a small per- 

 sistent axis, the nut-like carpels compressed laterally, produced on the back into 

 large chartaceous or coriaceous reticulated obovate wings thickened on the lower 

 margin. Seed solitary by abortion, or rarely 2 in each cell, ovate, compressed, 

 irregularly 3-angled, ascending obliquely, without albumen ; seed-coat mem- 

 branaceous, the inner coat often fleshy ; embryo conduplicate ; cotyledons thin, 

 foliaceous or coriaceous, irregularly plicate, incumbent or accumbent on the 

 elongated descending radicle turned toward the hilum. 



A family of two genera, one widely distributed, the other, Dipteronia, dis- 

 tinguished by the broad wings encircling the mature carpels, and represented 

 by a single Chinese species. 



1. ACER, L. Maple. 



Characters of the family. 



Acer with sixty or seventy species is widely distributed over the northern hemi- 

 sphere, with a single species extending south of the equator to the mountains of Java. 

 Acer produces light close-grained moderately hard wood valued for the interior 

 finish of houses and in turnery. The bark is astringent, and the limpid sweet sap of 

 some of the American species is manufactured into sugar. 



Acer is the classical name of the Maple-tree. 



CONSPECTUS OF THE NORTH AMERICAN SPECIES. 



1. Leaves simple. 



*Flowers appearing with or after the leaves from terminal buds ; fruit ripening in the 

 autumn. 

 Flowers with petals, appearing- after the leaves. 



Flowers in erect dense racemes ; leaves 3 or slightly 5-lobed. 



1. A. spicatum (A). 

 Flowers in drooping racemes. 



Ovary and young fruit glabrous ; leaves 3-lobed at the apex. 



2. A. Pennsylvanicum (A). 

 Ovary and young fruit hairy ; leaves deeply 5-lobed. 



3. A. macrophyllum (G). 

 Flowers in terminal pendent corymbs. 



Leaves palmately 7-9-lobed. 4. A. circinatum (B, G). 



Leaves 3-lobed or 3-parted. 5. A. glabrum (B, F, G). 



Flowers without petals, appearing after the leaves, in nearly sessile umbel-like ter- 

 minal and lateral j>ndent corymbs. 

 Corymbs sessile. 



