AOEBACEAE. 205 



10. Leaf-scars with a membranous wing at top. 11. 

 Leaf -scars not winged: twigs purplish. 



(Vine maple). A. circinatum. 



11. Scales blunt: buds and twigs usually green. A. japonicum. 

 Scales mucronate: buds and twigs purplish. 



A. Sieboldianum. 



12. Exposed scales about four. 13. 

 Exposed scales six or more. 23. 



13. Leaf-scars meeting in a point. 14. 

 Leaf-scars connected by a transverse line. 20. 



14. Buds gray-hairy: leaf-scars with minute red glands 



above. (Box elder). 15. 

 Buds glabrate: leaf-scars not glandular. 18. 



15. Twigs very glaucous. 16. 



Twigs little if at all glaucous, or else puberulent. 17. 



16. Twigs green when rubbed. (2). A. Negundo. 

 Twigs violet when rubbed. A. Negundo violaceum. 



17. Twigs olive, puberulent. A. Negundo interius. 

 Twigs bright green, glabrous. A. Negundo Nuttallii. 



18. Twigs moderate (4 mm.): buds large. 



(Norway maple). A. platanoides. 

 Twigs slender (3 mm.) : buds small. 19. 



19. Bud-scales purplish, brown-bordered. A. pictum. 

 Bud-scales light brown. A. truncatum. 



20. Twigs woolly near the end. 



(Woolly red maple). A. Drummondii. 

 Twigs glabrous. 21. 



21. Buds collaterally multiple toward spring. 22. 

 Buds always solitary. 27. 



22. Bark of trunk rough but not flaking. 



(Red maple). (3). A. rubrum. 

 Bark flaking, leaving brown areas. 



(Silver maple). A. saccharinum. 



23. Buds ovoid, usually very blunt. 24. 

 Buds conical or acute. 29. 



