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CLIMATIC CYCLES AND TREE-GROWTH 



V. Kidder, who has been conducting excavations in the ancient ruins 

 there. The rings in these specimens are rather erratic and only one 

 gave a reliable record back to about 1720. 



Raton, New Mexico (R) — This is a collection of three increment- 

 borings secured near the highway over Raton Pass. Only one proved 

 datable. 



Nebraska (NEB) — This is a group of 12 sections from young 

 trees sent by Mr. Jay Higgins, forest supervisor, at the request of Dr. 

 F. E. Clements, from the plantations on the Nebraska Forest and from 

 the native yellow-pine stands near the Niobrara Division of the forest. 

 The three yellow-pine specimens all cross-identify nicely and give a 

 record extending back to the middle 1880 's. The jack pines, except 

 one, are also reliable in dating and extend back to about 1907. The 

 three Scotch pines extend back to about 1913, but do not cross-identify 

 in a way to give confidence. 



In the study of western cycles a group from Nebraska would be 

 very valuable, but it should go back 100 years at the least for proper 

 comparison with the other western groups. The above specimens, 

 however, will be most useful in climatic comparisons. 



Wind River, Washington (WR) — This group was collected June 

 20, 1925, at the Wind River Forest Experiment Station, Washington, 

 a most favorable location on a tributary of the Columbia River, per- 

 haps 75 miles from Portland. Five increment-borings were obtained, 

 one yellow pine and the rest Douglas fir. Most of these were erratic in 

 growth, perhaps from injuries, and one, at least, was too much crushed 

 in boring. So the group was not used in the special study of western 



cvcles. 



NORTH AMERICAN GROUPS 



American Arctic (AA) — These 21 sections, chiefly white pine and 

 fir, came from high latitudes in the MacKenzie River area of northern 

 Canada, by courtesy of Hon. Chas. Camsell and Mr. G. S. Hume, 

 Department of Mines, Ottawa, at the request of Mr. V. Stefansson, 

 the explorer. They were mostly cut in 1923. The interesting and 

 gratifying fact is that they can be cross-identified for the most part 

 and dated. The growth is usually very small and sometimes erratic. 

 The 21 specimens are divided into three subgroups, as follows: 



