PINUS 



37 



b. Leaves 2 in a fciscicle, or in 2's and 3's 

 c. Cone-scales unarmed 



d. Leaves 2-4 cm, long; cones 



often curved 

 d. Leaves 3-17 cm. long; cones 



usually not curved 



e. Leaves 7-17 cm. long; 

 cone -scales without a 

 central protuberance 



e. Leaves 3-7 cm. long; 

 cone -scales with a tall 

 central protuberance 



c. Cone-scales armed 



d. Leaves in 2's and (often) 3's 

 on the same tree 



e. Leaves 7-13 cm, long; 



prickle weak 

 e. Leaves 3-7 cm. long; 



prickle very strong 



d. Leaves 2 in a fascicle 



e. Leaves 2-4 cm, long 

 e. Leaves 4-17 cm. long 



f. Leaves 4-8 cm. long; 



native tree 

 f. Leaves 7-17 cm. long; 



introduced tree 



9. P. banks iana 



2. P. resinosa 



4. P. sylvestris 



5. P. echinata 



8. P. pungens 



9. P. banksiana 



6. P. vLrginiana 

 3. P. nigra 



1. P^ strobus L. White Pine. A large forest tree 20-50 m. 

 high, with a trunk diameter of 6-13 dm. ; bark on the young bran- 

 ches smooth, on the old trunks divided by shallow grooves into 

 wide flat-topped ridges; leaves in 5's, 7-13 cm. long, slender, 

 marked with white lines, the fascicle-sheaths deciduous; mature 

 cones slender, cylindrical, somewhat curved, 1-1. 5 dm. long, the 

 scales unarmed. Rich woods, Newfoundland to Manitoba, south to 

 Iowa and the mountains of Georgia and Tennessee (Fig. 9). 



2, _P. resinosa Ait. Red Pine. A tall forest tree reaching a 

 maximum height of 50 m. and a diameter of 15 dm, ; bark reddish. 



