20 BULLETIN 691, 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 intelligently 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 



