5O PlNACEAE. 



8. Needles blue-green. P. sylvestris. 

 Needles yellow when young. P. sylvestris aurea. 



9. Needles rather short (under 8 cm.). 10. 

 Needles rather long (over 9 cm.), dull. 12. 



10. Twigs glaucous. P. viginiana. 

 Twigs not glaucous, u. 



11. Tree. P. montana. 

 Round shrub. P. montana Mughtis. 



12. Trees. 13. 



Shrub. P. nigra pygmaea.. 



13 Pyramidal. P. nigra. 



Round-topped. P. nigra austriaca. 



14. Bark orange. P. nigra cebennensis.. 

 Bark rather red : needles glossy. P. resinosa. 



15. Needles moderately long (under 15 cm.). P. rigida. 

 Needles very long (over 15 cm.). P. Taeda. 



16. Twigs glabrate. 17. 



Twigs tomentose. P. Cembra. 



17. Trees. 18. 

 Dwarfed. 19. 



18. With spreading branches. P. Strobus. 

 With ascending branches. P. Strobus fastigiata. 



19. Needles very glaucous. P. Strobus alba. 

 Not very glaucous. 20. 



20. Bush-like. P. Strobus brevifolia. 

 Umbrella-shaped. P. Strobus umbraculifera. 

 Prostrate. P. Strobus prostrata. 



SCIADOPITYS. Umbrella Pine. 



Evergreen percurrent trees with ductless soft white wood 

 without resin passages; moderate fluted buff twigs swollen at 

 intervals ; continuous pith ; no stipule scars ; alternate persistent 

 ciliate scales whorled at the swollen nodes and each then with 

 a long linear phylloid shoot in its axil ; monoecious catkin- or 

 cone-like naked flowers ; and cones with several-seeded scales. 

 ''Leaves" green, grooved, revolute. S. verticillata. 



