68 BULLETIN 623, U. S. DEPARTMENT OF AGRICULTURE. 
The following notes regarding some of the methods of compiling 
Table III may assist the reader in understanding it. 
During the season of 1910 when these investigations were begun, 
the fruit of the several sizes was not separatea* into the Orchard and 
Standard grades and no record of the fruit of the Cull grade was made 
in securing the data, but in determining the average annual produc- 
tion of cull fruit the 6-year period was used as a basis, so that the 
results would be comparable with the averages for the other grades 
and the total crop. 
Variable fruits were first recorded during the season of 1912. In 
succeeding years the observers gradually became familiar with an 
increasing number of forms of such variations and recorded them as 
they were observed. This accounts for the general increase from 
year to year in the number of such fruits recorded in these lists. 
This increase in the number of variable forms observed and recorded 
results in a lower average than would have been the case if all the 
forms had been recognized and recorded for the entire period of the 
investigation. 
In expressing the averages of weights in these tables it was found 
impracticable to retain more than one decimal. The exact decimal 
expression of ounces as a fractional part of a pound extends to four 
places, but only one decimal place has been retained. In expressing 
the averages for the number of fruits occurring in different groups, no 
decimal has been retained except when the average number is less 
than unity. Hence, it will be found that the totals of averages will 
sometimes vary slightly from the average of the totals of the corre- 
sponding numbers. 
The fruits of the Cull grade are not assorted into sizes, and on this 
account the total figures for the weights and numbers of fruits of the 
various sizes represent only the commercial crops of the trees. 
A very heavy freeze occurred over most of the citrus sections of 
southern California in the winter of 1912-13, resulting in more or less 
injury to the foliage or trees in many groves. In nearly all localities 
many mature fruits on the trees were frozen, so that they became 
partly dry and hollow. Where it was possible to distinguish the 
frozen fruits from the sound ones they were assorted into the Cull 
grade, which accounts for the large number of cull fruits in the rec- 
ords of many of the trees for the year 1913. 
In order to show the method of interpreting these individual-tree 
performance records and of applying the knowledge gained from them, 
the following discussion is presented of the data recorded from repre- 
sentative high and low producing trees of the Washington strain. 
The records of tree No. 7: 2-37-1, listed in rank 11 in Tables II 
and III, show it to have produced an annual crop during the 6-year 
period averaging 298.8 pounds, and except for the reduced yield in 
the year of the freeze it produced a fairly uniform quantity each 
