46 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. Ill 



7. The variations among the trend coefficients and ratios of op- 

 posed trends of individual trees emphasized again the locaHzed influ- 

 ence of site factors on the single tree, the so-called microsite factors. 



8. Correlations between tree growth and rainfall of stations other 

 than Chacon gave mixed and rather poor results. Certain regional 

 tendencies remained, but they are of little or no value. 



9. Correlations between tree growth and Las Vegas rainfall were 

 higher for the period 1910-1941 than for that of 1893-1941. 



10. General correlations between tree growth and Santa Fe rainfall 

 were fair to poor and have little value as regards season-to-season 

 fluctuations. Such results were to be expected in view of the distances 

 involved and the areal dififerences in rainfall as measured from station 

 to station. 



11. The higher the correlations were among the trees themselves, 

 the higher their correlation with rainfall. An increase in amount of 

 rainfall was accompanied by greater agreement among the trees. 



12. The most important information brought out by the correlation 

 of tree growth and Santa Fe March-July rainfall for the periods 

 1850-1897, 1898-1941, and 1910-1941 was this: The quality of the 

 correlations was lowest for the first period and highest for the last. 

 All tree groupings conformed. The amounts of March- July rainfall 

 at Santa Fe showed a similar increase for the three periods. 



13. In the above correlations, the trees from the wetter sites 

 showed not only the highest correlations but also the greatest increases. 



14. A change in temperature that affected the time of growth ini- 

 tiation in the spring probably shifted the month-interval of rainfall 

 to which the trees responded. 



15. Trees from drier sites, as a group, were poor recorders of 

 changes in rainfall characteristics ; individually, two out of the four 

 conformed in part to the wet-site group. 



16. A summary of changes from the period 1850-1897 to the 

 period 1 898-1 941 follows: 



In March- July rainfall : 



Average variation, average departure, and average departure from mean 

 variation decreased with an increase in average rainfall. 

 In tree growth: 



Among all trees, internal agreement increased. 



For dry-site trees, group 10, average variation, average departure, and 

 average departure from mean variation increased. 



For all trees, group 7, average variation and average departure increased 

 whereas average departure from mean variation decreased. 



For wet-site trees and group 7 (restricted), average variation, average de- 

 parture, and average departure from mean variation decreased, thus agree- 

 ing with changes in March-July rainfall. 



