626 



TREES OF NOHTH AMERICA 



Leaves pale or glaucous beneath. 



Leaves dark green above, glabrpus beneath at maturity, their lobes coarsely 

 toothed or rarely entire. 6. A. Sacchaium (A, C). 



Leaves pale pubescent beneath, their lobes short and obtuse. 



7. A. Floridanum (C). 

 Leaves green beneath. 



Leaves yellow-green above, more or less hirsute-pubescent, especially be- 

 neath and on the petioles, their lobes entire or undulate, the liasal sinus 

 often closed by the overlapping lobes. 8. A. nigrum (A). 



Leaves tomentulose or rarely glabrous beneath, their lobes slightly lobulate, 

 sometimes acuminate. 9. A. leucoderme (C). 



Corymbs short-stalked ; leaves pale and usually pubescent beneath, o-lobed, the 

 lobes distinctly lobulate, acute or obtuse. 



10. A, grandidentatum (F, H). 



**Flowers appearing before the leaves in umbel-like fascicles from separate lateral buds ; 



fruit ripening in spring or early summer. 



Flowers sessile or short-stalked, without petals ; ovary and young fruit tomentose ^ 



leaves deeply 5-lobed. 11. A. saccharinum (A, C). 



Flowers on long pedicels, with petals ; ovary and young fruit glabrous ; leaves 3-5- 



lobed. 12. A rubrum (A, C). 



2. Leaves pinnately or ternately divided ; flowers dioecious, without petals. 



13. A. Negundo (A, C, F, G). 



1. Leaves simple. 

 *Flowers appearing with or after the leaves- fruit ripening in the autumn. 



1. Acer spicatum, Lam. Mountain Maple. 



Leaves subcordate or sometimes truncate at the base, conspicuously 3-nerved, 3 

 or slightly 5-lobed, with gradually narrowed pointed lobes, and sharply and coarsely 



Ii^ J09 



glandular-serrate, when they unfold puberulous on the upper and densely tomentose 

 on the lower surface, and at maturity membranaceous, 4'-5'' long and broad, turning 

 in the autumn to various shades of orange and scarlet; their petioles slender, enlarged 

 at the base, 2'-3' long, often becoming scarlet in summer. FloTvers opening in June 

 after the leaves are fully grown, on slender pedicels ^'-f in length, \' in diameter, 

 the pistillate toward the base and the staminate at the apex of narrow many-flowered 



