191 



variation in its organs than any other genus of trees found in this 

 State. The leaves may be simple or compound, large or small, smooth 

 or hairy. The twigs may be green, brown, or red. The -flowers may 

 be in small lateral clusters, in long terminal racemes, or in drooping 

 clusters; appear before, with, or after the leaves. Their color may 

 be green, yellow, or red. The fruit, while similar in all the species 

 so far as type is concerned, varies considerably in size, divergence 

 of the wing, and arrangement. Their habitat also varies, some like 

 the Ked Maple, preferring moist locations, while the Mountain Maple 

 frequents rocky situations. In addition to these general differences 

 among the species, a greater difference becomes evident as one 

 studies the detailed description of the species which follow: 



SUMMER KEY TO THE SPECIES. 



Page. 



1. Leaves simple, v 2 



1. Leaves pinnately compound, A. Negundo 197 



2. Leaf petioles with acrid milky sap, A. platanoidles 198 



2. Leaf petioles without acrid milky sap .3 



Flowers in terminal racemes 



Flowers in lateral clusters, appearing before or with the leaves 



4. Flowers appear with the leaves A. Pseudo-platanus 198 



4. Flowers I appear after the leaves, 5 



5. Flowers in erect racemes; leaves coarsely serrate and usually 3-lobed, — A. spicatum 193 



6. Flowers in drooping racemes; leaves finely terrate, 3-lobed at apex, at first brown 



pubescent beneath, A. pennsylvanioum 192 



6. Flowers opening before the leaves,, the drooping fruit ripening in spring or early 

 summer, 7 



6. Flowers opening with the leaves, drooping fruit ripening in summer or early 



autumn, A. saccharum 194 



7. Flowers with petals; leaves bright green above, pale green nearly glabrous beneath 



3-5-lobed; fruit keys incurved A. rubrum 196 



7. Flowers without petals; leaves green above whitish or silvery beneath, deeply 



5-lobed; fruit keys divergent, A. saccharinum 195 



WINTER KEY TO THE SPECIES. 



1. Buds stalked with few exposed scales, ; 2 



1. Buds sessile or nearly so, with G or more exposed scales, 4 



2. Buds evidently-staiked ; bark streaked longitudinally with white lines, 



A. pennsylvanicum 192 



2. Buds short-stalked; bark not streaked longitudinally with white lines, 3 



3. Buds small, 1/5 of an inch long including stalk; twigs reddish-brown to dingy 



gray; pith brown, A. spicatum 193 



3. Buds large, ovoid, the terminal one acute the lateral obtuse and closely appressed; 



twigs greenish-purple and glaucous; pith light, .A. Negundo 197 



4. Buds with 8-16 exposed scales, brown, scute, non-collateral, leaf-scars nearly 



encircle stem, A. saccharum 194 



4. Buds with 6-8 exposed scales, red or green, obtuse 5 



5 Terminal buds small, generally less than 1/5 of an inch long; terminal and lateral 

 buds of same size; collateral buds present, 6 



6. Terminal buds large, generally over 1/5 of an inch long; terminal buds larger 

 than lateral; collateral buds absent, 7 



6. Twigs red and lustrous; bark rough but not flaking in large pieces, A. ruhrum 196 



6. Twigs bright chestnut-brown; bark falling away in thin large flakes, A. saccharinum 195 



7. Buds red; leaf -scars encircle stem; lenticels scattered; lateral buds appressed; 



bark black, fissured, not scaly, A. platanoides 198 



7. Buds green; leaf -scars do not encircle stem; lenticels numerous; lateral buds pro- 

 jecting; bark brownish and scaly, A. Pseudo-platanus 198 



