44 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. Ill 



7. Correlations among different trees and among dift"erent groups 

 were distinctly lower for the period 1850- 1897 than for the period 

 1898-1941. 



8. A simultaneous comparison of trend among all trees yielded 

 9 complete agreements among the trees during the 48 years of the 

 period 1850-1897 and 15 during the 44 years of the period 1898-1941. 



9. For group 10 (dry sites) average year-to-year variation, aver- 

 age departure, and average departure fromi mean variation increased 

 whereas for group 11 (wet sites) they decreased for the period 1898- 

 194 1 in contrast with the period 1850- 1897. However, the average 

 departure of two of the trees in group 10 actually agreed with 

 group II. 



10. The average departure from mean variation of group 7 (re- 

 stricted) and group 7 itself decreased for the period 1898-1941 in 

 contrast with the period 1850-1897. 



11. A study and comparison of the growth-layer sequences em- 

 phasize the role of site factors local to each tree and the striking 

 contrast of characteristics between the two periods, 1850- 1897 and 

 1898-1941. 



Study of rainfall characteristics. — i. Chacon rainfall was correlated 

 with that of the other six stations for eight different month-intervals. 

 Trend coefficients ranged from 0.61 to 0.99 and ratios of opposed 

 trends from 0.41 to 0.09. 



2. No clear-cut pattern emerged from this correlation between 

 Chacon and the other stations. However, the values declined with 

 the presence of summer rainfall and with an increase in the number 

 of months in the month-intervals. Within the area from which rain- 

 fall stations were drawn, distance from Chacon made little difference 

 in the variations among the several stations. 



3. The average trend coefficient between Chacon and the other 

 stations was approximately 0.89 and the ratio of opposed trends 0.23. 

 If the trees were responding directly to the rain falling at the im- 

 mediate site, they may be expected to correlate with Chacon rainfall 

 to a degree equaling or slightly exceeding (because of the distance 

 involved) the average of the correlations between Chacon and the 

 other rainfall stations. 



4. Correlations among the eight different month-intervals at Chacon 

 ranged from —0.33 to 0.99 for the trend coefficients and from 0.66 

 to 0.06 for the ratio of opposed trends. Such divergences demanded 

 that tree growth be tested against the full series of month-intervals. 



