ACER 



a. Bud -scales 2, valvate 



b. Buds glabrous, thick, blunt, 



8-10 mm. long 

 b. Buds puberulent, short, slender, 



5 mm. long 



a. Bud-scales more than 2 



b. Buds red, brown, or black; 

 twigs not green 



c. Terminal buds usually 5 mm. 



or more long;sap milky 

 c. Terminal buds usually less 



than 5 mm. long; sap clear 



d. Buds brown or black; 

 scales 6 or more 



e. Twigs glossy-buff or red- 

 dish-brown;buds dark, 

 glabrate 



e. Twigs dull straw-color, 

 smooth and shiny, with 

 somewhat prominent len- 

 ticels ; buds straw-color, 

 hairy 



d. Buds reddish or orange; 

 scales about 4 



141 



1. A. pensylvanicum 



2. A. spicatimi 



3. A. platanoides 



4. A, saccharum 



5. A. nigrum 



e. Twigs bright chestnut- 

 brown; inner bark with a 

 rank odor 



e. Twigs red and lustrous; 

 inner bark not rank 



7. A. saccharinum 

 6. A. rubrum 



b. Twigs green; buds covered with a 

 dense white pubescence 



8. A. negundo 



1. A. spicatum Lam. Mountain Maple . Shrub or small tree 

 up to 10 m. high, with thin, rather smooth, brown or grayish- 

 brown bark mottled with dingy gray patches; yoxmg twigs grayish- 

 pubescent; buds short- stalked, small, about 5 mm. long; terminal 

 buds larger. Cool woods, Newfoundland to Saskatchewan, south to 

 Iowa, Ohio, and the mountains of Georgia and Tennessee (Fig. 194). 



2. A. pensylvanicimi L. Striped Maple . Moosewood. A small 

 tree up to 10 or 12 m. high, with smooth bark, becoming conspic- 



