WINTER KEY TO THE SPECIES OF PINUS 
a. Leaves 5 in a cluster; cones 4-10 inches long.............. 
SORES Solis bawiumccnauekiure weet NG Seateee P. strobus, p. 7. 
aa. Leaves 2 in a cluster; cones less than 4 inches long. 
b. Leaves 1-3 inches long. 
c. Leaves about 1 inch long, divergent; cones sessile, point- 
cc. 
ing forward towards the tip of the branch, persistent 
10-15 years, opening very unevenly...P. banksiana, p. 9. 
Leaves 144-3 inches long, slightly divergent; cones stout- 
stalked, pointing away from the tip of the branch, 
maturing in second season, opening evenly............. 
cialp RE Brot BARC aR USER Rela doth Tee MAE P. sylvestris, p. 13. 
bb. Leaves 3-6 inches long. 
c 
cc. 
Bark of trunk red-brown; cones maturing in second 
season, about 2 inches long; cone-scales thickened at the 
apex, but unarmed..............200005 P. resinosa, p. 15. 
Bark of trunk gray to nearly black; cones maturing in 
first season, 2-3 inches long; cone-scales thickened at the 
apex and topped with a short spine................... 
CRE AL Ashlea great Mascara lave! P laricio austriaca, p. II. 
