ACERACEAE 741 



Flowers in lateral clusters : 



Clusters expanding before the leaves, sessile or nearly so, not drooping. 



Petals wanting or obsolete : ovary pubescent. 1. A. saccharinum. 



Petals present : ovary glabrous. 



Leaf-blades glabrous or glabrate beneath : samaras less than 4 cm. long : 



wings rather spreading. 2. A. rubrum. 



Leaf-blades copiouslv woolly beneath : samaras over 4 cm. long ; wings 



nearly contiguous. 3. A. Drummondii. 



Clusters expanding with the leaves, drooping. 



Trunks with grav or nearly black bark : samaras mostly over 3 cm. long. 



Leaf-blades scarcely paler beneath than above : lobes entire or undulate. 4. A. nigrum. 

 Leaf-blades pale or glaucous beneath : lobes coarsely toothed. 5. A. Sacchantm. 



Trunks with white bark : samaras mostly less than 2.5 cm. long. 



Leaf-blades glaucous and sometimes pale-pubescent beneath : samaras 



light green. 6. A. Floridanum. 



Leaf-blades green and velvety beneath : samaras red. 7. A. leiicoderme. 



Flowers in terminal racemes or panicles. 



Flowers in panicles : petals linear or linear-spatulate, twice or thrice as long 



as the sepals : samaras less than 2.5 cm. long. 8. A. spicatum. 



Flowers in racemes : petals oblong, about as long as the sepals : samaras over 



2.5 cm. long. 9- A. Pennsylvanicum. 



1. Acer saccharinum L. A tree rarely 36 m. tall, with a maximum trunk diameter 

 of about 1.5 m., the bark flaky at maturity, gray, or that of the twigs reddish brown : leaves 

 appearing after the flowers ; blades about as long as broad, 10-15 cm. long, with 3-5 

 prominent incised lobes longer than the body, silky when young, glabrate, bright green 

 above, glaucous or silvery-white beneath, truncate or cordate at; the base : flower-clusters 

 sessile or nearly so : calyx greenish or yellowish : stamens exserted : fruit drooping : 

 samaras 5-6 cm. long, tomentose or glabrate at maturity, at length widely spreading. [A. 

 dasycarpum Ehrh. ] 



In woods and river swamps, New Brunswick to Ontario. North Dakota. Florida'and the Indian 

 Territory. Late winter and spring. Silver Maple. Soft Maple. White Maple. River Maple. 



2. Acer rubrum L. A tree, sometimes 35 m. tall, with a maximum trunk diameter 

 of about 13 dm., the bark fissured on the trunk, smooth and pale or white-gray on the 

 branches. Leaves appearing after the flowers ; blades as broad as long or often longer 

 than broad, deep green above, pale or glaucous and glabrate beneath, shallowly 3-5-lobed, 

 rather evenly serrate, rounded or subcordate at the base : flower-clusters dense, red or 

 yellowish, appearing before the leaves from the ends of short branchlets or in the axils of 

 last year's leaves ; the pistillate with longer pedicels than the staminate : sepals nearly dis- 

 tinct : petals narrower than the sepals : ovary glabrous or glabrate : fruit drooping from 

 the elongating pedicels, commonly red : samaras less than 4 mm. long, the wings diverging 

 at about 45 degrees. 



In low grounds and swamps, New Brunswick to Manitoba, Florida and Texas. Late winter and 

 early spring. Red Maple. Swamp Maple. WatePv Maple. Scarlet Maple. 



3. Acer Drummondii Hook. & Arn. A tree reaching a height of 26 m., with a max- 

 imum trunk diameter of about 1 m., the bark pale or whitisli, rough on the trunk. Leaves 

 appearing after the flowers ; blades varying from ovate to depressed orbicular in outline, 

 8-15 cm. broad or sometimes smaller, 3-lobed, coarsely and irregularly toothed, deep green 

 above, white and woolly beneath, rounded or cordate at the base : flower-clusters red, ter- 

 minating short branchlets in the axils of last year's leaves, the pistillate with longer 

 pedicels than the staminate : sepals nearly distinct, oblong or slightly narrowed upward : 

 petals nearly like the sepals only narrower : ovary glabrous : fruit drooping from the 

 slender pedicels : samaras over 4 cm. long, the wings tending to converge. 



In river swamps, Missouri to Georgia, Florida and Texas. Spring. Red Maple. 



4. Acer nigrum Michx. f. A forest tree sometimes 40 m. tall, with a maximum trunk 

 diameter of fully 1.5 m., the bark dark, coarsely flaky. Leaves appearing with the flowers ; 

 blades mainly broader than long, often 15-20 cm. broad, relatively thin, deep green above, 

 scarcely paler and more or less downy beneath, with 3-5 entire or merely undulate lobes, 

 sinus at the base closed at the overlapping lobes : pedicels drooping, pubescent when young : 

 calyx campanulate, about 5 mm. long : sepals rounded : petals wanting : fruit drooping : 

 samaras 3-4 cm. long, slightly spreading. 



In rich woods or open fields, Ontario to Minnesota, Georgia and Louisiana. Spring. Black Maple. 



5. Acer S^ccharum Marsh. A forest tree with a maximum height of about 40 m. 

 and a trunk diameter of 1.5 m., the wood firm, heavy, the bark usually separating in coarse 

 scales at maturity. Leaves appearing with the flowers ; blades firm, mostly with 5 sinuate 

 toothed lobes, 8-15 cm. in diameter, deep green above, pale or glaucous and tomentulose 

 at least when young, beneath, cordate with an open shallow sinus : pedicels villous, droop- 

 ing : calyx campanulate, about 5 mm. long : sepals obtuse : petals wanting : disk in the 



