20 BULLETIN" 697, U. S. DEPARTMENT OF AGRICULTURE. 
unusual climatic or other conditions which may have occurred 
during the period of study. Of course during long periods of observa- 
tion the effect of occasional extreme conditions is largely overcome, 
so that the records become more nearly an absolute guide. 
PRESENTATION OF DATA. 
The tables and diagrams here presented are prepared from the 
performance records of Marsh grapefruit trees in two plats, one of 
25 trees planted in 1898 and the other of 52 trees planted in 1903. 
For convenient reference in the following discussion these plats will 
be designated A and B, respectively. These records cover the six 
years from 1910 to 1915, inclusive. However, the culls were not 
recorded in 1910 or 1911, so that the data shown for the fruit of that 
grade represent conditions during four seasons only. In these 
plats there are representative trees of five of the six recognized 
important strains of the Marsh variety. In plat A, the older trees, 
there are 19 trees of the Marsh strain, 5 of the Seedy strains, and 1 
of the Rough strain. In plat B there are 40 trees of the Marsh strain, 
9 of the Alternate-Bearing strain, and 3 of the Unproductive strain. 
These plats are both located as solid blocks of trees in larger com- 
mercial plantings. It is interesting to note that only 76 per cent 
and 76.9 per cent, respectively, of trees of the Marsh strain were 
found in the two plats, and approximately the same proportions of 
typical Marsh trees are found in the two orchards as a whole. 
The performance records, descriptions, and illustrations from 
photographs here presented only partially indicate the character- 
istics of the various strains. The trees and fruits must be seen and 
studied personally before their true differences can be fully appre- 
ciated and the importance of these variations in commercial fruit 
growing really understood. On this account the determination 
of trees from which to secure bud wood for propagation should not 
be made entirely on the basis of the performance records of the 
trees. The most reliable selection will be made by a comparative 
study in the orchard of the performance records of the trees, the 
habits of growth and appearance of the trees, and the character of the 
fruit on the trees. Such a selection can be inteUigently made only 
by some one who, through close study and observation of the trees 
themselves, has gained an intimate knowledge of the interrelation 
of tree characteristics and crop production. 
In Tables III and IV are presented the individual-tree perform- 
ance records of all the trees in the investigational plats on which 
data have been secured for the 6-year period. These show the 
production by weight and number of fruits of each grade and size 
for each year and the average annual production for the 6-year 
period both by grades and sizes. The basis of ranking the trees in 
