NORTH AMERICAN MAPLES. 101 



maples the axillary buds are frequently accompanied by 

 globose collateral or even superposed buds which, however, 

 develop within the axils of the lowermost scales of the 

 main bud, and so represent branches of the normal axil- 

 lary branch, and not proper supernumerary buds. 



KEY TO THE SPECIES. 



* Buds evidently stalked, with few scales, these valvate in pairs 

 so that all but the outer two are concealed : leaf scars acute 

 margined : pith brown. — Bush Maples. 

 Buds large (6 to 10 mm. long exclusive of stalk), glabrous: twigs 

 glabrous, with a more or less developed decurrent line be- 

 tween the nodes : bundle scars often 5 to 7.... A. Pennsylvanicum. 

 Buds small (about 5 mm. long including the stalk). 



Twigs and buds glabrous, the latter plump A. glabrum* 



Closely gray pubescent, the buds slender A. spicatum. 



* * Buds not evidently stalked, the outer pair of scales separated, 



hairy-tufted at apex : leaf scars acute margined, their axils 

 more or less hairy : pith white or at length yellowish. — Vine 

 Maples. 

 Twigs and buds at first pubescent with long, loose hairs, and 



generally viscid A. circinatum. 



* * * Buds large, ovoid, the lateral appressed, not evidently stalked, 



but sometimes lengthening into short, leafless branches the 

 first year: exposed scales 6, or in reduced lateral buds only 2, 

 the lower pair fused at base: leaf scars meeting, glabrous. 

 Sycamore Maples. 



Twigs very stout, glabrous and glaucous: pith brownish: 



bundle scars 7 to 9 A. macrophyllum. 



* * * * Buds short stalked, often appearing sessile : exposed scales 6 or 



more, ciliate, several pairs not meeting at apex, but the outer- 

 most pair often fused below. 

 -*- Exposed scales 6 to 8, red or reddish, tomentose cUiate, the 

 lowest pair commonly deciduous in early winter, exposing a 

 collateral bud on either side : leaf scars of a given pair rarely 

 contiguous : pith pinkish. — Soft maples. 



Bark gray, falling away in large thin flakes on old trees : twigs 

 glabrous, reddish A. saccharinum. 



Bark whiter, rough on old trunks, but not flaking in large pieces. 



Twigs red, glabrous A. rubrum. 



Twigs tomentose above A. rubrum var. Drummondii. 



«*- 4- Exposed scales 8 to mostly 12 to 16, brown to nearly black, often 



with silky gray pubescence : no collateral buds : leaf scars acute 

 margined, each pair almost meeting by their outer angles, their 

 axUs commonly gray or yellow pubescent. — Sugar maples. 



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