84 TREES OF THE NORTHERN UNITED STATES 



j GENUS 25. ACER. 



Trees, or rarely shrubs, with simple, opposite, and almost 

 always palmately lobed leaves, which, in our species, are 

 always deciduous. Flowers small and usually dull-colored, 

 in clusters. Fruit double-winged and 2-seeded, in some 

 species hanging on the tree till the leaves have fallen ; 

 in others dropping off early in the spring. The species 

 differ much in the spreading of. the wings of the fruit. 

 Wood light-colored and medium hard ; bark rather 

 smoothish, but in large trees with longitudinal cracks. 



* Leaves slightly or not lobed 13. 



* Leaves about 3-lobed (rarely 5-lobed); shrubs or small trees. 

 (A.) 



A. Leaves serrate 1,2. 



A. Leaves somewhat sinuate, not at all serrate; juice milky. 10. 



* Leaves 5-, rarely 3-lobed. (B.) 



B. The lobes acute, irregularly but quite fully serrate; juice not 

 milky. (C.) 



C. The fruit in corymbs, dropping early; American species. 



(D.) 

 D. Leaf -notches somewhat rounded; tree large; limbs 



drooping on old trees 3. 



D. Leaf -notches acute ; tree small . 4. 



C. Fruit in hanging racemes, remaining on the tree till au- 

 tumn ; leaves thickish 5. 



B. The lobes acute ; sparingly or not at all serrate. (E.) 



E. Juice not milky 6. 



E. Juice milky at the bases of the leaves 8, 9. 



B. The lobes obtuse and sinuate 10. 



* Leaves 5- to 7-lobed. (F.) 



F. Lobes fully serrate ..11. 



F. Lobes sparingly serrate. (G.) 



G. Juice milky 8, 9. 



G. Juice not milky ; leaves 8 to 10 in. broad 7. 



F. Lobes somewhat sinuate, not serrate ; juice milky 10. 



* Leaves with 7 or more lobes 11, 12. 



1. Acer spic&tum, Lam. (MOUNTAIN MAPLE.) Leaves with 3 

 (rarely 5) coarsely serrated, taper-pointed lobes, with slightly cor- 

 date base; downy beneath. Flowers greenish-yellow, in erect, 



