TREES xiii 



A. USUALLY SEEN AS TREES. 



1. Evergreen: unarmed except as 1 the simple leaves may be 



pungently pointed or toothed; or some leaflets may 

 be spine-like or the petioles with stout prickles. 2. 

 Deciduous. 33. 



2. Leaves needle-like or narrow, in terminal whorls on short 



spurs that are sheathed with scales. 3. 

 Leaves not in scale-sheathed clusters. 4. 



3. Needles 1-5, angular, in a rather erect cluster, p. 9. Pinus. 

 Leaves numerous, flat, spreading. p. 10. Sciadopitys. 



4. Leaves alternate or in crowded clusters. 5. 

 Leaves opposite, small or very narrow. 25. 



Leaves in whorls of 3. p. 14. Juniperus. 



Leaves alternate. 



5. Leaves small or very narrow. 6. 

 Leaves relatively large or broad. 15. 



6. Leaves 4-sided or 4-grooved. 7. 



Leaves not 4-sided, or if so neither clustered nor from 

 raised bases. 9. 



7. Leaves often clustered on short spurs. p. 8. Cedrus. 

 Leaves not clustered on spurs. 8. 



_^8. Leaves green, not disarticulating. p. 11. Cryptomeria. 

 Leaves often glaucous, disarticulating. p. 6. Picea. 



9. Leaves green on both sides. 10. 

 Leaves white-lined beneath. 11 



10. Leaves elongated, narrowed at base. p. 4. Taxus. 

 Leaves short and sharp, sessile. p. 11. Sequoia. 



11. Leaves decurrent in ridges on the twigs. 12. 

 Leaves not at all decurrent. 14. 



12. Leaves mostly serrulate above. p. 6. Tsuga. 

 Leaves entire. 13. 



13. Leaves sessile, 4-ranked; fruit a cone. p. 11. Sequoia. 

 Leaves narrowed at base, elongated. p. 5. Torreya. 



