18 KEY, EASED UPON FRUIT. 



C?. 2 Covered with spines ; dehiscent by 4 valves. 



Nuts sharply three-angled, 2 together, involucre soft-prickly. 



16. FAGDS FERRUGINEA. 

 Nuts subovoid, flattened, 1-3 together, involucral spines very sharp and 



hard 40. CASTANEA VESCA, var. AMERICANA. 



c. 2 Small, ovoid-lanceolate pods arranged in catkins, opening by two valves and 



containing numerous seeds furnished with silky down; leaves 

 d. Orbicular-ovate; petioles flattened; leaves 



Dentate 18. POPULUS GRANDIDENTATA. 



Finely serrate, sharply pointed 72. P. TREMULOIDES. 



Sinuate-toothed, tomentose beneath 96. P. ALBA. 



Obscurely-serrate, with obtuse or rounded apex. 97. P. HETEROPHYLLA. 

 <. 2 Ovate, closely serrate, whitish and reticulate-veined beneath. 



47. P. BALSAMIFERA. 



d. 3 Deltoid-ovate 48. P. MONILIFERA. 



c?. 4 Broadly deltoid 73. P. DILATATA. 



d. & Linear-lanceolate, tomentose on midrib above and petiole. 



45. SALIX NIGRA 

 d. 6 Lanceolate or elliptic-lanceolate, smooth above; capsules 



Sessile or nearly so 46. SALIX ALBA var. VITELLINA. 



With slender pedicels 71. S. AMYGDALOIDES. 



C 3 . Linear compressed pods, opening by two valves. 



80. ROBINIA PSEUD ACACIA 

 c 4 . Subcylindrical pods, long (10-12 in.), opening by two valves. 



89. CATALPA BIGNONIOIDES. 



c 5 . Ovoid, 5-valved capsule 102. GORDONIA LASIANTHUS. 



c 6 . Subovoid follicle with seeds suspended -by funiculi when ripe. 



106. XANTHOXYLUM CLAVA-HERCULIS. 



fit 2 . Aggregated fruit composed of many carpels, either closed or opened and co- 

 hering or closely massed together, forming a 

 b. Cone. 



C. Scales of the cone open carpels (Coniferce). 

 d. Scales many, persistent and spreading at maturity, each subtended by a 



bract ; ovules 2, inverted. 

 . Maturing the year after flowering (Pinus). 

 f. Cones oblong-ovoid, scarcely 2 in. long ; scales armed with 

 g. Weak prickles; leaves 3-5 in. long; prickles directed 



At about right angles to axis of closed cone 75. P. MITIS. 



Forward at 45 or less from axis 123. P. GLABRA. 



gr 2 . Stronger prickle ; leaves 1-2| in long 98. PINUS INOPS. 



/ 2 . Cones ovoid-pyramidal ; carpellary scales thickened at the apex and 

 g. Unarmed (smooth); cones 



2 in. in length, straight 19. PINUS RESINOSA. 



Less than 2 in., curved 99. PINUS BANKSIANA. 



fir 3 . Armed with a recurved prickle; cones about 



2 in. long; prickle strong 50. C. RIGIDA. 



2.3 in. long, with weak prickle, and 



wide-pyramidal; leaves in 3's 121. P. SEROTINA. 



Narrow pyramidal; leaves in 2's 122. P. CLAUSA. 



3-6 in. long, glossy brown; leaves in 2's and 3's. 125. P. CUBENSIS. 

 6-10 in. long; leaves in 3's 124. P. PALUSTRIS. 



