ie: 
PRELIMINARY STUDIES ON THE YELLOW PINE. 21 
NUMBER OF TREES NECESSARY FOR RELIABLE RESULTS. 
In seeking the best curve of tree-growth which a given locality 
can supply, it might be thought at first that a very large number of 
trees must be obtained in POP ie iw eke S* ee oe Oe 
order to get an average, 
but experience has shown x 
that the number may be | ® cho 213 N 
very small. In order to Tl 4 = 
test the accuracy ob- a 
hare n a 
careful cross-identifica- 
tion. Averages were then g 
obtained of the oldest 5, |, ia = -P =f ma 
AKL | UA feo 
0 
a 
a) 
> 
as 
. 
id 
groups and small. Of the 
original 25 trees in the |. 
first Flagstaff group, 19 | s4~ a z1 
were subjected to very P| 
i 
W 
I 
tained from a small num- 
ber of trees,acomparison | s.3>>:: zal 
was made between large 
going back about 400 F 
~ years, the oldest 10 (350 
years), the oldest 15 (300 muh 
“Fj | 
mediately evident that 5 |* , 
trees gavealmost the same 
years), and the entire 19 : 
growth as 15, even to 
small details. Between | *piNi-| ue AR 
of the oldest 2 was carried 
back fully 500 years. On 
plotting the groups of 15, 
10, and 5 with its exten- 
sion of 2, it became im- as 
6 
years. Finally, the record : 
cee 
or 
a 
y an \ 
TESS 
ol 
£ 
ts 
reaching back only 200 
these 5 and the oldest 2 
taken by themselves the 
» agreement was not quite 
so perfect, yet was soclose | .| a5+--+ 
ia 
2-18 
Iz 
Co, 
1 
that errors thus intro- 
duced would not affect 
the curves. It must not 
be taken for granted estar) | Beko Sp 
without test that this re- | a °B “AK 
markable agreement be- t [ 
sh. Ss Sh, ose oS 
a very small gr ‘oups © Monthy precictation in inchesteoid lines) ae 
of trees is true necessarily Fig. 2.—Monthly and yearly precipitation at Prescott and 
for other trees or even for _ size and character of rings. 
