166 Proceedings of the Ohio State Academy of Science 



3. Leaves without stipules. 4. 



4. Leaves with much milky sap in the petiole, glabrous, dark green 



above, lighter below, usually with 7 prominent palmate veins ; 

 flowers corymbose, unfolding with the leaves : wings of the fruit 

 diverging nearly in a straight line ; petals present ; winter buds 

 rounded. A. plataiioides. 



4. Leaves with watery or frothy sap, pale and nearly glabrous beneath, 



usually with 5 prominent palmate veins ; flowers corymbose, un- 

 folding with the leaves ; wings of the fruit diverging a little less 

 than a right angle; petals none; winter buds pointed. A. saccha- 

 rum. 

 o. Leaves very sharply and finely serrate, 3-lobed at the outer end, 

 widest above the middle, the lobes abruptly narrow-acuminate, 

 brown pubescent below when young ; twigs green, striped with 

 darker lines; flowers racemed, terminal, unfolding after the leaves. 

 A. pennsylvanicum. 



5. Leaves dentate-serrate or lobed, not abruptly narrow-acuminate; 



twigs not striped. 6. 



6. Leaves broadly 3-5-lobed, the lobes rather regularly and continuously 



dentate-serrate or dentate-crenate ; flowers racemed, terminal, un- 

 folding after the leaves. 7. 



6. Leaves usually with 3-7 slender, long and pointed lobes, the lobes 



irregularly or interruptedly serrate or serrate-dentate; flowers in 

 dense sessile lateral clusters, appearing before the leaves. 8. 



7. Leaves longer than wide, slightly 3-lobed at the outer end, usually 



only very slightly lobed at the lower end, not glaucous below ; 

 bark of twigs green or grayish ; racemes erect ; a shrub, rarely 

 a small tree. A. spicatum. 



7. Leaves as broad or broader than long, prominently 5-lobed, glabrous 



and dark green above, pubescent and light glaucous below, on 

 long reddish petioles ; bark of twigs reddish-brown ; racemes 

 drooping ; wings of fruit pubescent, moderately spreading ; a large 

 tree. A. pseudo-platanus. 



8. Leaves usually deeply 5-lobed, lobes slender, acute, white and glaucous 



beneath ; notches between the lobes often somewhat rounded ; 

 fruiting pedicel short and stiff, 1-2 in. long ; wings divergent ; 

 petals none. A. saccharinum. 

 8. Leaves sharply 3-5-lobed, whitish glaucous beneath, notches acute; 

 fruiting pedicel long, slender and drooping, 2-4 in. long; wings 

 incurved ; petals present. A. rubrum. 



I. Acer saccharinum L. Silver Maple. A large tree 

 with flaky bark, the twigs often reddish, self-pruned by basal 

 joints. Leaves deeply 5-lobed, the lobes rather narrow, acumi- 



