conifers. 8ILVA OF NORTH AMERICA. 13 



CONSPECTUS OF THE NORTH AMERICAN SPECIES. 



Strobus. Cones subterminal ; apophysis of the cone-scales thin, usually unarmed ; leaves in clusters 

 of five, their sheaths loose and deciduous ; fibro-vascular bundle 1. Wood light-colored, soft. 

 White Pines. 



Eustrobi. Resin ducts peripheral. 



Wings longer than the seeds ; leaves sharply serrulate, denticulate toward the apex. 

 Hypoderm or strengthening cells of the leaves not surrounding the resin ducts. 



Leaves slender, glaucous, from 3 to 4 inches in length ; cones 5 or 6 inches long ... 1. P. Strobus. 

 Leaves thick, rigid, from 1 \ to 4 inches in length ; cones from 5 to 11 inches long . 2. P. monticola. 



Hypoderm or strengthening cells of the leaves numerous, surrounding the resin ducts. 



Leaves stout, rigid, from 3£ to 4 inches in length ; cones from 12 to 18 inches 



long 3. P. Lambertiana- 



Wings much shorter than the seeds ; leaves mostly entire, or denticulate toward the apex. 



Leaves slender, from 3^ to 4 inches in length ; cones from 5 to 9 inches long, their 



scales reflexed 4. P. strobiformis. 



Leaves thick, rigid, from 1^ to 3 inches in length ; cones from 3 to 10 inches long, 



their scales thickened, light brown, pointed at the apex 5. P. flexixis. 



Leaves thick, rigid, from 1^ to 1\ inches in length ; cones oval or subglobose, from 

 \\ to 3 inches long, their scales much thickened, dark purple, terminating in stout 



incurved nearly triangular tips 6. P. albicaulis. 



Pinaster. Apophysis of the cone-scales thickened, usually armed; leaves in clusters of 1 to 5, their 

 sheaths usually persistent. Wood resinous. Pitch Pines. 

 Resin ducts of the leaves peripheral. 



Integrifolise. Cones subterminal ; leaves entire, their sheaths deciduous ; fibro-vascular bundle 1. 

 Cone-scales thick, unarmed ; seeds large, their wings minute. Leaves in 1 to 5-leaved 

 clusters. Nut Pines. 



Leaves stout, glaucous, in 1 to 5, usually in 4-leaved, clusters, from \\ to \\ inches in 



length ; cones from \\ to 2 inches broad 7. P. quadrifolia. 



Leaves slender, in 2 or 3-leaved clusters, from 1-i- to 2 inches in length ; cones from 1 



to 2 inches broad 8. P. cembroides. 



Leaves stout, tipped with rigid spines, in 1 or 2-leaved clusters, from 1^ to 1\ inches 



in length ; cones from 1^ to 1\ inches long 9. P. monophtlla. 



Leaves stout, rigid, sharp-pointed, in 2 or 3-leaved clusters, from f of an inch to \\ 



inches in length ; cones from 1^ to 1 \ inches long 10. P. edulis. 



Cones dark purple, their scales somewhat thickened at the apex, armed with slender prickles ; 

 seeds shorter than their wings ; leaves in crowded clusters of five, rigid, incurved. 



Leaves from 1 to \\ inches in length; cones subcylindrical, from Z\ to 5 inches long, 



their scales armed with minute incurved prickles 11. P. Balfouriana. 



Leaves from 1 to 1^ inches in length ; cones from 3 to 3^ inches long, their scales 



armed with long slender awn-like prickles 12. P. aristata. 



Sylvestres. Cones subterminal ; leaves serrulate, their sheaths persistent ; fibro-vascular bun- 

 dles 2. 



Leaves in 2-leaved clusters, slender, dark green, from 5 to 6 inches in length ; cones 

 ovate-conical, from 2 to 1\ inches long, their scales slightly thickened, unarmed, seeds 



much shorter than their wings 13. P. resinosa. 



Resin ducts of the leaves parenchymatous. 



Ponderosse. Cones subterminal, their scales conspicuously umbonate ; leaves in 2, 3, or 5-leaved 

 clusters, their sheaths persistent, or deciduous in No. 17 ; fibro-vascular bundles 2. 

 Leaves in 5-leaved clusters. 



Leaves stout, dark green, from 9 to 13 inches in length ; cones broadly ovate, long- 

 stalked, from 4 to 6 inches long, their scales much thickened, with broad reflexed 



umbos 14. P. Torretaka. 



Leaves stout, dark green, from 5 to 7 inches in length; cones oval, from 2 to 2^ 



inches long, their scales armed with small recurved spines . 15. P. Arizonica. 



