20 BULLETIN 460, U. S. DEPARTMENT OF AGRICULTURE. 



The foliage of adult trees is a dark yellowish green, while that of 

 seedlings is a bright bluish green. Each season's growth of leaves 

 remains on the branches for nearly 9 years, though a good many 

 leaves fall during the fourth summer. The leaves are borne in clus- 

 ters of 2, occasionally of 3 (Pis. XI, XII). They are sharp pointed, 

 often curved, and vary in length from about seven-eighths of an inch 

 to nearly If inches. The margins of the leaves are smooth (without 

 minute teeth). In cross section the leaves show two resin ducts. 



The yellowish-brown and somewhat shiny cones (PL XI) are from 

 about 1| to nearly If inches long. They ripen in August and Sep- 

 tember and shed their nutlike edible seeds (PL XI, 5) during the 

 latter part of September and in October, the very short rudimentary 

 wings (from one-eighth to one-sixth of an inch long) remaining at- 

 tached to the cone scales (PL XI, a) when the seeds fall. Unexposed 

 parts of the cone scales are pale red-brown. The perfect seeds, 1 borne 

 only by scales in the middle of the cone, are pale yellow with reddish- 

 brown specks and mottlings on one side and dull red-brown on the 

 other. Most of the empty cones fall from the trees during the first 

 winter or earLy the following springs The seed-leaves (PL XII, a, h) 

 vary in number from 7 to 10. 



The wood of Pinus edulis is narrow-ringed and hard, but very 

 brittle. The thin layer of sapwood is nearly white, and the heart- 

 wood is light yellowish brown. Next to that of Pinus cembroides it 

 is the heaviest of Rocky Mountain pine woods, a cubic foot of dry 

 wood weighing nearly 40 pounds. It is used largely for fuel, ties, 

 fence posts, and other local purposes. 



OCCURRENCE AND HABITS. 



Pinus. edulis grows on dry foothills, mesas, mountain slopes, and 

 sides of canyons, at elevations between 5,000 and 9,000 feet, or occa- 

 sionally somewhat below 5,000 feet (Map No. 6). It is usually found 

 in poor, rocky, gravelly soils, but often in shallow or deep layers of 

 gravel and sand overlying rock, and sometimes in the crevices of 

 rocks. Very commonly, it is associated with western yellow pine, 

 one-seed juniper, Utah juniper, mountain mahoganies. Gambel oak, 

 and mountain red cedar. Its most frequent associates are, however, 

 the one-seed and Utah junipers. Occasionally it forms pure stands of 

 limited extent. The largest growths occur on mesas and elsewhere 

 at the lower elevations noted, where the sandy or gravelly soil 

 deposited by washing is moderately rich. 



Piiion is very intolerant of shade in all but the seedling stages of 

 its growth, a period when partial shade assists the young plants to 



1 Indians and settlers gather large quantities of 1he seeds; the former use' them largely 

 for food, and the latter send them to eastern and other city markets as sweetmeats. 

 Birds and squirrels and other rodents, however, claim a large share of piiion seeds, many 

 of which are devoured before tne cones open. 



