118 DOUGLASS— CHARACTERS IN ANNUAL RINGS OF 



last instrument as many as 34 curves of 500 points each have been 

 tested in one clay for all periods between 5 and 32 points ; in this the 

 curves were taken entire or in any number of parts. 



At the present development of the investigation a review of the 

 topographic effects observed in the trees seemed necessary. For such 

 purpose a group of some 21 sequoias which had grown in Redwood 

 Basin, 15 miles east of General Grant National Park, Fresno County, 

 California, was used. It is understood that these trees had been cut 

 down, and that radial pieces were cut from the stumps, shipped to 

 the laboratory at Tucson, and there identified and measured. The 

 trees were scattered for a mile along a valley whose steep slope was 

 toward the north. The upper end is near the top of the mountain, 

 but a spring supplies a small stream of water. The upper trees 

 mostly had a very dry soil, while those below, some 600 or 700 feet in 

 vertical measurement, had more level ground and greatly increased 

 moisture. The average growth per century in the last 500 years was 

 about J.(y cm. The least was less than 4 cm. and the greatest was 

 over 15 cm. The big-growing trees were mostly close to the water- 

 course in the lower basin. The average growers were mostly around 

 the edges of the basin, while the slow-growing trees were chiefly at 

 the tops of the slopes. All this was as expected. Three larger 

 growing trees close to the upper limit formed interesting exceptions. 

 One was an infant sequoia, only 700 years old when cut, and there- 

 fore naturally a fast-growing tree. Another at the very highest point 

 was about fifty yards above the spring and undoubtedly tapped an 

 underground flow of water leading to it. Its type of rings was very 

 similar to those in the basin. The third exception had very large 

 rings, but they were full of sensitive variations like the slow-growing 

 trees near by. That tree is probably over a pocket of water whose 

 help increased its growth, but which failed in extremely dry condi- 

 tions. It is evident, then, that with the sequoias moisture may control 

 the growth up to a maximum fully four times as large as the 

 minimum. 



The type of ring and its adaptation to identification and study 

 varies greatly with the moisture supply. The large rings of the 

 quick -growing trees are either very complacent — that is, of the same 



