The Trees of Vermont 25 



SUMMER AND WINTER KEY TO THE SPECIES OF PINUS 



a. Leaves 5 in a cluster; cones 4-10 inches long ... .P. strobus, p. 27. 

 aa. Leaves not 5 in a cluster ; cones less than 4 inches long. 



b. Leaves 2 in a cluster ; cone-scales unarmed, or at most provided 

 with minute prickles. 



c. Leaves less than 4 inches long (about 1 inch), strongly diver- 

 gent ; cones pointing forward towards the tip of the branch, 

 persistent 10-15 years, opening very unevenly, 



P. banksiana, p. 31. 

 cc. Leaves 4-6 inches long, not strongly divergent ; cones not point- 

 ing forward towards the tip of the branch, not persistent 10- 

 15 years, but opening in the autumn of the second season and 



falling the next summer P. resinosa, p. 33. 



hb. Leaves 3 in a cluster ; cone-scales armed with conspicuous 

 prickles P. rigida, p. 29. 



