FOREST TREES OF THE PACIFIC SLOPE. 



61 



OCCURRENCE. 



Confined to slopes, bluffs, and ridges. Grows well in coast sand and also heavier inland 

 soils. Short lived in arid situations, but does not thrive in wet soils. On coast, occasion- 

 ally mixea with Monterey and Gowen cypresses ; inland, forming interrupted pure forest, 

 occasionally with groups of California swamp pine in moist placeB. 



Climatic Conditions. — Seasonal temperature from 25° to 95° I\ Annual average pre- 

 cipitation, not over 17 inches, and wholly rain. Close proximity of range to sea gives 

 humid air, while at least one-third of days are cloudy or foggy. 



Fig. 21. — J'inus radiata, open cone: a, seed. 



Tolerance. — Very tolerant, growing in pure, dense stands, where trunks clean them- 

 selves well and trees maintain good crown cover, under which humus accumulates rapidly. 

 Isolated trees usually retain low side branches, with heavy foliage until old age. 



Reproduction— Prolific annual seeder. Seed with very high rate of germination and 

 persistent vitality. Produces cones at early age. Long persistent and closed cones shed 

 seed only after several years; often opened only by fire, which is followed by very dense 

 reproduction, particularly in exposed mineral soil. 



15188—08 5 



