6 KEY, BASED UPON FLOWERS. 



/*. Becoming succulent in the fruit 63. MORUS RUBRA. 



e 3 . Ovary 1-celled and many-seeded, the seeds at maturity furnished 



with a hairy tuft (Salicacece) . 



f. Bracts of the catkins entire ; calyx wanting ; stamens 2-7 (Salix) ; 

 catkins on leafy branchlets with 



g. Pallid villous dentate scales 140. S. LAEVIGATA. 



gr 2 . Yellowish deciduous scales ; capsules glabrous ; stamens 3-5 ; 



petioles 

 h. Glandular ; scales of catkins entire ; leaves 



Narrow-lanceolate ; fruiting catkins rather dense. 



45. S. NIGRA. 

 Lanceolate or ovate lanceolate, glaucous beneath, fruiting 



catkins very loose 71. S. AMYGDALOIDES. 



Tfc 2 . 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. 



7i 2 . Ovate-orbicular, coarsely dentate, beneath 



Glabrous at maturity 18. POPULUS GRANDIDENTATA. 



Densely tomentose at maturity 96. POPULUS ALBA. 



h 3 . Deltoid; branchlets terete 73. P. DILATATA. 



f/ 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. 



2 . Gymnpspermae seeds naked, borne superficially on carpellary scales ; cone- 

 bearing (Conferee) ; scales 

 b. Many, imbricated, 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 (awn less) ; leaves 



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



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



e 2 . Armed with a prickle ; leaves 

 /. li-2i in. long; cones 1-3 in 



Very oblique, branchlets brown and rough 148. P. CONTORTA. 



Not oblique, branchlets purple, quite smooth 98. P. INOPS. 



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



f z . 3-5 in. long, sheaths elongated, cones 



g. Scarcely 2 in. in length, solitary or in pairs and slightly if at all 



oblique ; branchlets. 

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



when closed 75. P. MITIS. 



Smooth ; prickle inclined more towards the apex of the cone. 



123. P. GLABRA. 



f/ 2 . 2-3^ in. long, mostly in umbels, very oblique. .170. P. MURICATA. 

 d*. Leaves in 3s and scales of cone thickened at apex and armed with a 



prickle ; leaves 

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



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



e 3 . 7-10 in. long, stout; cone 3-5 in. long, sessile. . ..147. P. PONDEROSA. 

 e 4 . 8-15 in. long ; cones 



6-10 in. long, sub terminal, slightly if at all oblique. 



124. P. PALUSTRIS. 



10-15 in. long, lateral, very oblique and heavy. . .169. P. COULTERI. 

 d 3 . Leaves in 5s with very short sheaths ; cones longer than the leaves and 



with scales not thickened at the ends, unarmed ; cones 

 4-6 in. long 49. P. STROBUS. 



