298 



THE CULTIVATED EVERGREENS 



1. Winter-buds brown. 



J. Cones deciduous: winter-buds resinous: 

 leaves 2, their sheath about % inch 



long ._ 



Jj. Cones tenaciously persistent: winter- 

 buds not resinous: leaves sometimes 3, 



sheath up to 1 inch long 28. 



II. Winter-buds grayish-white, cylindric, not 



resinous 27. 



HH. Resin-ducts marginal: leaves light green: 



branchlets orange 22. 



EE. Leaves in clusters of 3, or 2 and 3 (2 in No. 32 and 

 shoots multinodal) : spring-shoots often multinodal. 

 F. Resin-ducts of leaves medial. 



G. Young cones subterminal: shoots uninodal. 

 H. Branchlets orange: cones 3-6 inches long. . . .29. 

 HH. Branchlets glaucous: cones 5-15 inches long. 30. 

 GG. Young cones lateral: shoots multinodal. 

 H. Length of leaves 3-5 inches. 



I. Bark of branches and trunk rough: leaves 



2 or 3 in a cluster 31. 



n. Bark of branches and of upper part of 



trunk smooth: leaves always 2 32. 



HH. Length of leaves 6-9 inches 33. 



FF. Resin-ducts internal, leaves 8-18 inches long. 

 G. Winter-buds whitish: cone dull brown, 6-10 

 inches long: spring-shoots usually uninodal. .34. 

 GG. Winter-buds light brown: cone lustrous brown, 



3-63^2 inches long: spring-shoots multinodal .35. 

 DD. Cones tenaciously persistent, often serotinous (opening 

 one or several years after maturity): leaves with 

 medial resin-ducts (marginal in No. 36): spring- 

 shoot multinodal and cones lateral (in Nos. 36 and 

 37 sometimes uninodal). 

 E. Leaves in clusters of 2. 



F. Resin-ducts of leaves marginal: cone with obtuse 



umbo 36. 



FF. Resin-ducts medial. 



G. Strobiles (cones) symmetrical. 



H. Length of leaves 5-8 inches 37. 



HH. Length of leaves 1-33^2 inches. 



I. Prickles of cone stout 38. 



II. Prickles of cone slender. 



J. Cones remaining closed for many years . 39. 



JJ. Cones opening at maturity 40 



GG. Strobiles (cones) unsymmetrical. 

 H. Length of leaves less than 4 inches. 



I. Cone not prickly, curved 41 



n. Cone prickly, straight and sometimes 



symmetrical 42 



HH. Length of leaves 4-6 inches: cone with stout 



and large prickles 43, 



26. P. nigra 



P. sinensis 

 P. Thunhergii 

 P. resinosa 



P. ponderosa 

 P. Jeffreyi 



P. echinata 



P. glabra 

 P. TcBda 



P. palustris 

 P. caribcea 



P. halepensis 



. P. Pinaster 



P. pungens 



P. clausa 

 P. virginiana 



P. Banksiana 

 P. contorta 

 P. muricata 



