SUMMARY 



The foregoing book includes the following descriptive matter : 



1. The technique of collection and preparation of material brought 

 up to the latest development, with special studies of trees and rings. 



2. New instruments constructed and used, namely, the tubular 

 borer, the automatic plotter, the longitudinal plotter, and the White 

 cyclograph (periodograph without the attachment for producing the 

 periodogram) ; the cyclogram is here definitely used in place of the 

 periodogram. 



3. The collection of long tree-records including (a) sequoia groups 

 from Calaveras and Springville, (b) coast redwood groups from Santa 

 Cruz and Scotia, (c) a 640-year yellow pine, and (d) much archaeo- 

 logical material for constructing a very long yellow-pine growth record. 



4. The collection and measurement of 305 yellow-pine ring records 

 in 42 groups, from 10 western mountain states, representing the area 

 from the eastern slope of the Rockies to the Pacific coast and extending 

 from the Mexican border to the latitude of the Columbia River. 

 Practically all these trees were standardized individually before obtain- 

 ing group averages. 



The results obtained and described are as follows : 



1. All the sequoia groves from Calaveras to Springville give the 

 same climatic record and can be cross-identified throughout their 

 records; the northern groves are more complacent in ring- type. 



2. The coast redwoods, carefully selected and most carefully com- 

 pared, could not be cross-identified and therefore are not used. 



3. Ten-inch boring tests every 20 feet on a sequoia 265 feet long 

 and 15 feet in diameter, which fell in 1901, gave almost perfect simi- 

 larity throughout in the heartwood, but very considerable differences 

 in the water-soaked sapwood. The problem of change in ring-size 

 is opened. In living trees the change is probably very small and con- 

 nected with conservation of moisture, sometimes possibly retroactive 

 on the rings. 



4. Topographic studies show that soil moisture is a strongly con- 

 trolling factor in ring-type, both in sequoia and yellow pine. Soil- 

 moisture gradient below the trees could be used as an indicator of ring 

 characters. 



5. Trees at higher altitudes and at higher latitudes (than about 

 32° N.) show more complacent rings. 



6. Close grouping in the pines and sequoias produces objectionable 

 alterations in rings only under extreme conditions and can be avoided 

 with trifling care in selection of trees. 



7. Deficient soil-depths and denudation of soil about trees pro- 

 duce intensely compressed outer rings in the pines of dry areas, and 

 this character can be recognized in much prehistoric material. 



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