42 BULLETIN" 327, U. S. DEPARTMENT OE AGRICULTURE. 



of equal age, which favor overhead light to all of the trees. It en- 

 dures but little side shade, as is shown by the long, clean trunks it 

 produces in close stands and commonly also even in rather open 

 stands. Ability to endure shade, however, appears to vary with the 

 nature of the soil, available moisture, and climatic conditions, trees 

 always showing relatively greater tolerance of shade under the best 

 conditions for growth. 



Shasta red fir seeds plentifully, good crops of cones being pro- 

 duced about every two or three years. Seed production is usually 

 greatest in the more open stands of moderately old trees. The seed 

 has a fairly high rate of germination, but under ordinary conditions 

 of storage its vitality is retained for only a few months. Germina- 

 tion occurs abundantly on moist mineral soil in the open or under 

 light shade, being much less frequent or wanting on dry, thick duff. 

 Seedlings grow rapidly in cool, moist, sandy soil, soon restocking 

 high slopes and openings cleared by fire or storm. 



LONGEVITY. 



Shasta red fir appears to be rather long lived. Trees from 20 to 36 

 inches in diameter are from 225 to 370 years old. Very large trees, 

 not yet studied chiefly because the timber is not now cut for mill- 

 ing, would certainly show much greater ages. There are evident 

 differences, not yet determined, in the longevity of trees growing on 

 high, exposed slopes and those at lower levels in more protected 

 places, trees of higher elevations naturally being considerably older 

 than those of the same diameter growing at lower levels. 



KEY TO GENERA. 



Leaves four sided; cones hanging down or curved downward, the cone 



scales firmly attached and not falling away when the cones are ripe_ Picea. 



Leaves flat, grooved on the upper side; cones upright, the cone scales 

 (asily detachable and falling away from a persistent spikelike central 

 stem when the cones are ripe Abies. 



KEY TO PICEA. 



Twigs smooth: 



Leaves very keenly pointed and stiff; cones mostly 3 to 4 inches 



long Picea parryana. 



Leaves only moderately sharp-pointed ; cones mostly 1J to 2\ inches 



long Picea, canadensis. 



Twigs minutely hairy : 



Cones firmly attached to the twigs and persistent for a number of 



years* * Picea mariana. 



Cones lightly attached to the twigs and soon falling from the 



trees Picea engelmanni. 



