6 KEY, BASED UPON FLOWERS. 



8 . Not glandular; scales dentate 46. S. ALBA. 



/*. Bracts of the catkins lacerately fringed; calyx a disk-like cup; stamens 



8-30, leaves broad (Populus); styles with 



g. Narrow lobes ; capsule small ; seeds minute, petioles laterally com- 

 pressed; leaves 



h. Cordate-orbicular, finely serrate 72. P. TREMULOIDES. 



h*. Ovate-orbicular, coarsely dentate, beneath 



Glabrous at maturity 18 POPULUS GRANDIDENTATA. 



Densely tomentose at maturity 96. POPDLUS ALBA. 



h z . Deltoid; branchlets terete 73. P. DILATATA. 



gr 2 . Broad lobes ; capsules large ; seeds 1 line or more in length and 



leaves 

 Acuminate, smooth, strongly reticulated and whitish beneath. 



47. P. BALSAMIFERA. 



Obtuse or rounded at apex, tomentose at least along the veins 



beneath 97. P. HETEROPHYLLA. 



Broadly deltoid; branchlets angled 48. P. MONILIFERA. 



O?* Gymncspermae seeds naked, borne superficially on carpellary scales. Cone- 

 bearing (Coniferce) ; cones with 

 b. Many imbricated scales, each in the axil of a bract and bearing 2 inverted 



ovules ; seeds winged. 



C. Leaves evergreen, fascicled ; cones maturing the second year (Pinus). 

 d. Leaves in 2s ; cones with scales 

 e. Smooth (awnless) ; leaves 



5-6 in. long, with long sheaths 19. P. RESINOSA. 



1 in. or thereabouts in length, sheaths short .99. P. BANKSIANA. 



C 9 . Armed with a prickle ; leaves 



/. 2-3 in. long ; cone 2-2| in. long 122. P. CLAUSA. 



f* t 3-5 in. long ; sheaths elongated ; branchlets 



Rough ; prickle inclined nearly at right angle to the axis of cone 



when closed 75. P. MITIS. 



Smooth ; prickle inclined towards the apex of the cone. 



123. P. GLABRA. 



/*. lf-2 in. long ; sheaths short 98. P. INOPS. 



ci 2 . Leaves in 3s and scales of cone thickened at apex and armed with a 

 prickle ; leaves 



3-6 in. long, cone about 2 in. long ; prickles strong 50. P. RIGIDA. 



5-8 in. long ; cone 2-3 in ; prickles weak 121. P. SEROTINA. 



8-15 in. long ; cone 6-10 in. long 124. P. PALUSTRIS. 



<p. Leaves in 5s with very short sheaths ; cones longer than the leaves and 



with scales not thickened at the ends, unarmed 49 P. STROBUS. 



d 4 . Leaves in both 2s and 3s, 7-12 in. long; cone 3-6 in. long, glossy, brown. 



125. P. CUBENSIS. 

 C 9 . Leaves evergreen, scattered (not fascicled) ; cones with thin scales, maturing 



the first year (Abies'). 

 d. Cones erect, cyclindrical, large (3-4 in.); leaves 



flat, linear ... 22. A. BALSAMEA. 



tP. Cones pendant and bracts inconspicuous. 

 e. Small, 8 lines or less, scales entire at tip, leaves linear. 



21. A. CANADENSIS 



