26 



TREES AND SHRUBS 



I. PIN US L. Pine, Pin yon. 



Rigid, large sized trees 25 to 100 feet high or more, with 

 leaves in facicles of 2-5 surrounded at the base by scaly sheaths; 

 staminate aments at the ends of branchlets of the preceding year; 

 anthers 2-celled, pollen grains 3-celled the lateral 2 empty; pistil- 

 late cones globose or elongated, just back of the terminal bud or on 

 the young twigs; scales crowded, overlapping; cones maturing iho 

 second year, scales hard and woody, mostly tipped with a short 

 bristle or spine like appendage just below the apex; seeds winged. 



Leaves In fascicles of 2, short and curved, 3 to 

 4 cm. long; cone small, 4 to 5 cm. long 

 somewhat broader when mature and ex- 

 panded; seeds not winged. 1. p. edulis. 

 Leaves In fascicles of 3 to 5, longer than 4 cm. 

 (except In P. arlstata); seeds with at least 

 rudimentary wings. 

 Leaves In fascicles of 5. 



Cones 10 to 16 cm. long, the scales with 

 unarmed appendages; seeds with 

 only rudimentary wings; leaves 

 slender, not rigid, 4 to 8 cm. long. 

 Leaves entire 8. P. flexilis. 



Leaves serrulate 3. P. strobiformis. 



Cones 5 to 7 cm. long, tin scales with 

 armed appendages; seeds with con- 

 spicuous wings. 

 Leaves short and stout, 2 to 4 cm. 

 long, curved, crowded on the 

 branches; cone scales with long 

 and weak spines; cones 6 to 7 

 cm. long. 4. p. aristata. 



Leaves longer, 6 to 10 cm., not crowd- 

 ed; cone scales with short rigid 

 spines; cones 5 to 6 cm. long. 5. P. arieonica. 



Leaves In fascicles of 3 (rarely *4); append- 

 ages of cone scales short and stout. 

 Sheaths of the leaves persistent and con- 

 spicuous; leaves 10 to 25 cm. long; 



cones 7 to 15 cm. long. 6. P. brachyptera. 



Sheaths of the leaves deciduous; leaves 

 6 to 9 cm. long, rather slender; 

 cones 3 to 5 cm. long. 7. P. chihuahuana. 



2. PICEA Link. Spruce. 



Evergreen monoecious trees with soft wood, 30 — 75 feet high, 

 of conical form, leaves not fascicled, ascending or nearly erect, 

 short, quadrangular or nearly terete, with a prominent base which 

 remains after the leaves fall ; staminate aments from axils of leaves 



