24 WEST-AMERICAN 



No. 5 White Bark Pine - P. alttcaulis, Engelm. 

 Very white-barked, often depressed trees, forming 

 the timber line on certain peaks of the Sierra, Cas- 

 cade, and Rocky Mountains. Cone globular, set 

 close upon the short, stout, erect, white, annual stem. 



Peculiarities of the Alpine Pines. 

 Usually erect and aspiring, 15 to 30 feet, in the edge 

 of the alpine forest, these white-limbed trees often press 

 up along the glacier-graven, wind-swept passes of the 

 mountains, battling with eternal snows and sand-blasts, 

 until they become depressed, flat-topped and so close- 

 roofed with condensed branchlets and leaves that one 

 may walk as safely over them as upon a platform of 

 planks. These sylvan tables prepared in the wilder- 

 ness and just filling a rock basin to its rim are supported 

 from the downhill side by a single leg, a sturdy trunk, 

 only a few feet high, yet 12 to 18 inches thick; close- 

 grained and tough as hickory, and golden yellow with 

 accumulated pitch. Ring countings, by the aid of a lens, 

 reveal their ages, 500 to 800 years. Survivors of an 

 early generation, they are protected from the ruthless 

 enemy fire by their isolation and their half-yearly 

 tomb of ice. 



Sub-Genus 2. PINASTER. 



HARD-WOOD PINES. 



Cone-scales with exposed part (apophysis) generally 

 thicker than those of the other sub-genus; the pro- 



