ACERACEAE 



The Maples 

 Characteristics of the Genus Acer L. 



HABIT. Deciduous trees or shrubs, with handsome foHage, 

 usually assuming brilUan colors in autumn. 



LEAVES. Opposite; simple or compound; deciduous; peti- 

 oled; without stipules; simple leaves palmately 3-7-lobed; 

 compound leaves pinnate, with 3-7 leaflets. 



FLOWERS. Regular; polygamous, dioecious, or rarely per- 

 fect; small; borne either in lateral fascicles from separate flower 

 buds and appearing before the leaves, or in lateral and terminal 

 racemes, panicles, or corymbs and appearing with or after the 

 leaves; calyx colored, generally 5-parted; corolla usually 5-pet- 

 aled or absent; stamens 4-12, usually 7-8; ovary 2-celled, 

 2-lobed, compressed, with 2 styles; ovules 2 in each cell, as- 

 cending. 



FRUIT. Double samara united at base (key); each nut- 

 like carpel laterally compressed and produced into large, obo- 

 vate wing. Seed : usually solitary by abortion, ovoid, compressed. 



TWIGS. Slender to moderately stout; round; pith homo- 

 geneous, round; marked at base by bud scales with ringlike 

 scars; leaf scars more or less U-shaped, with 3 (rarely 5-7) 

 bundle scars. Winter buds: with valvate or imbricated scales, 

 inner scales accrescent, terminal buds larger than lateral. 



BARK. Astringent and variable. 



WOOD. Variable from soft to heavy and hard; diff'use- 

 porous; pores all small and not crowded; rays distinct on cross 

 section without lens; widely used for interior finish, etc., sap 

 of some species manufactured into sugar. 



SILVICAL CHARACTERS. Mostly tolerant; fibrous root 

 systems; widely used for ornamental and shade trees. 



GENERAL. This genus contains over 60 species of trees 

 widely scattered through the Northern Hemisphere with one 

 species extending into Sumatra and Java. In the United States 

 there are 13 native species. Several introduced species are planted 

 extensively, among these Norway and Sycamore maples are 

 very common and better known than many native species (both 

 are included in the key). 



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