ENUMERATION OF CONIFERS 301 



GG. Bloom of branchlets copious: leaves 5-8 inches 



long, pale bluish-green, rarely 2 30. P. Jeffrey i 



FF. Winter-buds resinous: leaves 6-12 inches long. . . .47. P. Coulteri 

 EE. Branchlets not glaucous (sometimes slightly so in 

 No. 33). 

 F. Length of leaves 6-12 inches. 



G. Resin-ducts internal; leaves in clusters of 2 and 



3 35. P. caribaea 



GG. Resin-ducts medial; leaves in clusters of 3. 



H. Color of leaves light bluish-green 33. P. Tceda 



HH. Color of leaves dark yellow-green 44. P. rigida var. 



FF. Length of leaves 3-7 inches. 



G. All leaves slender, about ^^-^ inch thick: bud- 

 scales with appressed tips. 

 H. Bark on trunk and branches rough: leaves 



grass-green, soft 45. P. radiata 



HH. Bark on upper part of trunk and on branches 

 smooth: leaves yellow or bluish-green, 



firm 46. P. attenuata 



GG. All leaves stout. 



H. Winter-buds ovoid, acute or acuminate, with 



appressed scales: leaves rounded on back. 29. P. ponderosa var 

 HH. Winter-buds oblong-ovoid, with spreading 



scales: leaves flat on back 44. P. rigida 



Number of leaves 2. 



c. Spring-shoots uninodal, with only one whorl of branchlets. 

 D. Bark of 2-4-year-old branchlets divided into con- 

 spicuous and sharply defined plates (the decurrent 

 base of the bracts), each peeling off as a whole. 

 E. Branchlets grayish- white: winter-buds not resinous, 



ovoid-oblong 25. P. leucodermis 



EE. Branchlets orange to bro^\^l or grayish-yellow. 

 F. Winter-buds brown. 



G. Young branchlets not bloomy: winter-buds 

 resinous. 

 H. Leaves with medial resin-ducts, their sheath 



about }i inch long 26. P. nigra 



HH. Leaves with marginal resin-ducts, their 



sheath about ^ inch long. 22. P. resinosa 



GG. Young branchlets bloomy: winter-buds not 



resinous : leaves sometimes 3 28. P. sinensis 



FF. Winter-buds grayish-white, cylindric-oblong, with 



conspicuously fimbriate scales 11. P. Thunbergii 



DD. Bark of 2-4-year-old branchlets not conspicuously 

 divided into plates, peeling off irregularly. 

 E. Length of leaves 1-3 J/^ inches. 



F. Leaves bluish-green or grayish-green: usually a 



tree 23. P. sylvestris 



FF. Leaves bright green: usually shrub 24. P. Mugo 



EE. Length of leaves 3-9 inches. 



F. Young branchlets bloomy: leaves slender, bright 



green 20. P. densiflora 



