Fam. 84. Aceraceae Juss. Maple Family 



Trees and shrubs with watery saccharine sap, polygamo-dioecious; leaves oppo- 

 site, simple and palmately lobed or pinnately divided; flowers small, regular, with 

 or without petals; ovary 2-celled, 2-lobed; ovules 2 in each cell. 



Three genera comprising about 200 species in the North Temperate Zone and 

 tropical mountains. 



1. Acer L. Maple 



Deciduous trees or rarely shrubs; flowers mostly 5-merous, in racemes, panicles 

 or corymbs; calyx colored, 5 (rarely 4 to 12) -lobed or -parted; petals either 

 none or as many as the lobes of the calyx, equal, usually with short claws, inserted 

 on the margin of a perigynous or hypogynous disk; stamens 3 to 12; ovary 

 2-celled, with a pair of ovules in each cell; styles 2, long and slender, united only 

 below, stigmatic down the inner side; back of each carpel bearing a wing, con- 

 verting the fruit into two 1 -seeded eventually separable samaras or "keys." 



Nearly 200 species in the Northern Hemisphere. 



Most of our species are used as street and shade trees, the ubiquitous A. 

 Negundo being extensively used in arid regions. Their buds, flowers and fruits 

 are eaten by many kinds of wildlife. 



I. Leaves compound, with 3 to 9 pinnately veined leaflets 1. A. Negundo. 



1. Leaves simple, palmately veined and mostly palmately lobed (2) 



2(1). Leaf margins smooth, not closely serrate; terminal and upper lateral lobes 

 of leaf with straight or concave sides, the lobes somewhat quad- 

 rate or squarish; base of sinus between lobes forming a rounded or 

 obtuse angle; the yellowish flowers and fruits produced along with 

 the leaves or after they develop; calyx bearded; fruit more or less 

 pubescent.. 2. A. barbatiim. 



2. Leaf margins more or less closely serrate; terminal and/ or at least the upper 



lateral lobes of the leaf with gradually rounded or tapering sides, 

 the lobes triangular; base of sinus between lobes forming an acute 

 angle; the reddish flowers and fruits produced before leaves de- 

 velop; calyx and fruit glabrous 3. A. rubrum. 



1. Acer Negundo L. Boxelder, ash-leaved maple, arce, fresno de Guajuco. 



Small tree with green pubescent to glabrous twigs and branchlets; leaves 

 pinnate, with 3 to 9 petiolulate very veiny and more or less pubescent leaflets, 

 when mature pubescent to glabrate beneath; leaflets 5-10 cm. long and 5-7.5 cm. 

 wide; terminal leaflet elliptic to obovate; lateral leaflets narrower and coarsely 

 few-toothed or entire; leaves of vigorous tips and sprouts with more numerous 

 often lobed leaflets; flowers greenish, unisexual, produced just before the leaves, 

 the staminate flowers fascicled and pendulous on filiform pedicels, the pistillate 

 flowers racemose; petals and disk absent; samaras 25-35 mm. long, yellowish, 

 strongly ascending, the seed prolonged. Rulac Negundo (L.) Hitchc. 



River banks, edge of springs, along streams, floodplain woods, waste places, 

 fencerows mainly in the e. half of Tex., Okla. (Bryan and Caddo cos.), N.M. 

 (widespread) and Ariz. (Apache to Mohave, s. to Cochise and Pima cos.), 

 Feb.-Apr.; from Fla. to Tex., n. to w. N.E., N.Y., s. Ont., and s.e. Minn.; much 

 cult, and naturalized e. to Maritime Provinces and e. Que. 



Those trees with the branchlets more or less permanently puberulent are 

 usually segregated as var. texanum Pax. 



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