12 KEY, BASED UPON LEAVES. 



Lanceolate, acute at base, minutely glandular and pubescent 

 beneath .................................... 37. C. AMARA. 



Oblong-lanceolate, glabrous, obtuse or rounded at base ; fruit a 

 samara, flat at base ............. 63. FRAXINUS SAMBUCIFOLIA. 



b z . Decompound Leaves. 



C. Petioles smooth and leaves 



d. Regularly bipinnate, leaflets sessile ............. 105. MELIA AZEDARACH. 



rf 2 . Regularly bipinnate excepting for the lowest pair of single leaflets ; 

 leaflets stalked ...................... 27. GYMNOCLADUS CANADENSIS. 



d z . Irregularly bipinnate, leaflets small and sessile, 



12-18 in number ..................... 109. GLEDITSCHIA MONOSPERMA. 



18-24 in number ..................... 27. GLEDITSCHIA TRIACANTHOS. 



C 9 . Petioles prickly, leaves large, with ovate, sessile, serrate leaflets. 



8. ARALIA SPINOSA. 

 a 8 . Subdeciduous Leaves a part only of the leaves falling in autumn, the rest 



remaining green through the winter. 



Obovate-spatulate, entire, shining green both sides . .118. QUERCDS AQUATICA. 

 a 3 . Persistent Leaves evergreen. 

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

 C. In fascicles of 



d. Two each, a membraneous sheath, inclosing the base of each fascicle, about 

 1 in. long, sheathes very short .................. 99. PINUS BANKSIANA. 



li-2 in. long, sheaths very short; branchlets purple. .98. PINUS INOPS. 

 2-3 in. long, slender with short sheaths ............ 122. PINUS CLAUSA. 



3-5 in. long, slender; branchlets 

 Rough ........................ . .................. 75. PINUS MITIS. 



Smooth ....................................... 123. PINUS GLABRA. 



5-6 in. long, thicker, sheaths elongated ........... 19. PINUS RESINOSA. 



<? 2 . Three each and 



3-6 in. long ...................................... 50. PINUS RIGIDA. 



5-8 in. long ................................. 121. PINUS SEROTINA. 



8-15 in. long .................................. 123. PINUS PALUSTRIS. 



e? 3 . Both two and three each ........................ 125. PINUS CUBENSIS. 



d*. Five each, sheath deciduous .............. ......... 49. PINUS STROBUS. 



C 2 . Not in fascicles (scattered), short, 4-angled and usually more or less curved ; 



branchlets 

 Pubescent ; leaflets rather thick ....................... 20. PICEA NIGRA. 



Smooth, leaflets slender . ............................. 100. PICEA ALBA. 



6 2 . Linear, flat and diverging in two directions. 



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



21. ABIES CANADENSIS. 

 c 2 . Subsessile, rigid and sharply bristle-pointed ..... 120. TORREYA TAXIFOLIA. 



C 3 . Sessile, entire, 8 lines or more in length ............ 22. ABIES BALSAMEA. 



b 3 . Scale-like or awl-shaped. 



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

 flat and two-edged branchlet .................. 24. THUYA OCCIDENT ALIS. 



c 2 . Scale-like, smaller, appressed in four ranks and making a rather 4-angled 



than flat branchlet ; fruit a 

 Small spherical cone ................... 74. CHAMAECYPARIS THYOIDES. 



Bluish berry .............................. 25. JUNIPERUS VIRGINIANA. 



