200 ACERACE^. 



pcrposed, sessile, attached to the inner angle of the cell by 

 nearly the whole length of one side, at length amphitropous 

 by a very broad insertion, the micropyle inferior. 



Fruit a donble samara ; the two carpels nut-like, coria- 

 ceous, flattish, at length separating from the small persistent 

 axis, indehiscent, the back produced into a large membrana- 

 ceous and reticulated wing, the lower margin of which is 

 thickened. Seed solitary, or rarely two, in each cell, as- 

 cending or nearly horizontal, destitute of a funiculus, com- 

 monly anatropous. Albumen none (the inner integument of 

 the seed often fleshy). Embryo conduplicate, sometimes 

 spirally convolute ; the cotyledons variously plicate or fold- 

 ed, sometimes rugose-complicate, foliaceous, or often fleshy 

 but foliaceous in germination, incumbent, oblique, or ac- 

 cumbent on the descending radicle. 



Trees, sometimes shrubs, with limpid or seldom rather 

 milky sap, terete branchlets, and scaly buds. Leaves oppo- 

 site, exstipulate, simple, or in one species palmately trisected, 

 palmately veined and usually lobed, deciduous. Flowers 

 small, greenish, yellowish, or red ; either in a terminal raceme 

 or panicle, appearing with or later than the leaves, or in fas- 

 cicles from separate lateral buds and preceding the leaves. 

 Pedicels not articulated. Bracts usually minute and caducous. 



Etymology. The classical Latin name of the Maple. 



PLATE 174. Acer saccharinum, Wangh.; — branch of a staminate 

 plant in flower, of the natural size ; with 

 1-3. Some details from Acer Pennsylvanicum, Linn., viz. : — 

 1. Diagram of a perfect flower. 2. A sterile flower, enlarged. 



3. A vertical section of the same, magnified, showing the perigynous disk. 



4. Sterile flower of A. saccharinum, enlarged. 



5. A stamen, more magnified. 



6. A fertile flower of the same species, magnified. 



7. Same, with the calyx laid open, showing the short stamens, disk, &c. 



8. The pistil of the same, the other organs removed. 



9. Vertical section of its ovary, more magnified. (Ovules advanced.) 



10. Fruit, of the natural size ; one carpel cut open to show the seed. 



11. A magnified seed vertically divided through the coiled cotyledons. 



12. Emhryo detached entire, a little imrollcd, magnified. 



