KEY, BASED UPON LEAVES. 33 



dd. Main ribs several palmately- veined. 



e. Ribs three at first, but soon five by branching; leaves alternate, tomen- 

 tose while young; base of petiole concave and fitting over the 

 axillary bud 13. PLATANUS OCCIDENTALS. 



ee. Ribs 5-7, from commencement ; leaves opposite, smooth , base of petiole sub- 

 tending (not covering) the axillary bud . . 7. ACER SACCHARINUM. 



CC. Needle-shaped without distinction of blade and petiole, short, about 1 

 in. in length, soft and in fascicles of many each. 



23. LARIX AMERICANA. 



bb. Compound Leaves. 



c. Palmate, with 7 obovate, serrate leaflets 6. AESCTLUS HIPPOCASTANUM. 



CC. Pinnate and with an odd terminal leaflet. 

 d. Glabrous and petiolate. 



e. Leaflets numerous, 21-41, each with one or two pairs of glandular teeth 

 at its base 4. AILANTHUS GLANDULOSUS. 



ee. Leaflets 7-9, ovate or lance-oblong, entire or very obscurely serrate. 



glaucous beneath 10. FRAXINUS AMERICANA. 





 dd. Pubescent, especially along the petioles and rachis; leaflets sessile. 



e. Leaflets ovate -lanceolate, finely serrate; pubescence of short, rust-colored, 

 clammy hairs 14. JUGLANS CINEREA. 



ee. Leaflets lanceolate-oblong, coarsely serrate; pubescence of copious, 

 longer and whiter hairs 5. RHUS TYPHINA. 



bbb. Decompound Leaves and very large, with ovate, sessile, serrate leaflets and 

 prickly petioles 8. ARALIA SPINOSA. 



aa. Evergreen Leaves remaining on over winter. 

 b. Needle-shaped and quite stiff, pointing every way. 



c. Long, 5 8 in., in fascicles of 2 each, a broad, membranous sheath enclosing 

 the base of each pair 19. PINUS RESINOSA. 



CC. Short, 8 lines or less, scattered (not in fascicles), 4-angled, usually more or 

 less curved 20. ABIES NIGRA. 



bb. Linear, small, flat and diverging in two directions. 



c. Petioled, obscurely denticulate, 8 lines or less in length. 



21. ABIES CANADENSTS. 



cc. Sessile, entire, 8 lines or more in length 22. ABIES BALSAMEA. 



bbb. Scale- like or awl-shaped. 



c. Imbricated and closely appressed in four ranks, but making a conspicuously 

 flat and two-edged branchlet 24. THUJA OCCIDENTALS. 



CC. Scale-like leaves, smaller, appressed in four ranks and making a rather 

 4-angled than flat branchlet. Awl-shaped leaves arranged in 

 whorls of three each 25. JUNIPERUS VIRGINIANA. 



5 



