8 BULLETIISr 813, U. S. DEPARTMENT OE AGEICULTURE. 



order that the results of the mdividual-tree studies might be truly 

 comparative. 



As a result of experience in similar work with other varieties, the 

 performance-record plats of Eureka lemons were located so that they 

 included representative trees of several important strains. The 

 records of the performance of these typical trees constitute the basis 

 for comparing the production of the different strains and their value 

 for commercial orcharding. 



The original plat included 105 trees. Later, additional trees 

 representing important strains were added, in order to secure as 

 complete information as possible concerning the variability of the 

 strains. By the selection of plats in uniform soil areas and in sections 

 with the same altitude, like exposure, and comparative drainage 

 conditions, it is believed that the results obtained are less affected by 

 fluctuations due to variations in soil fertility, soil moisture, and other 

 environmental factors than would be the case if the records of all of 

 the trees in the orchards were used for comparison. 



METHODS OF KEEPING PERFORMANCE RECORDS. 



The methods of keeping the individual-tree performance records 

 in the lemon plats were adopted as a result of the experience gained 

 during the preceding similar study of orange and grapefruit trees. 



These methods involve more detailed observations than is usually 

 considered necessary in commercial-orchard practice. A modification 

 of these methods, adapting them for regular lemon-tree record keep- 

 ing, is described in Farmers' Bulletin 794, entitled "Citrus-Fruit 

 Improvement: How to Secure and Use Tree-Performance Records." 



TREE NUMBERS. 



The individual lemon trees were given numbers so that the data 

 obtained from the study of each tree could be kept separate during 

 the entire period of observation. Each number consists of three parts 

 — -the number of the block in which the tree occurs, the number of 

 the row in the block, counting from some fixed point (as, for example, 

 the irrigation head), and the number of trees in the row. Where 

 several different orchards are under observation, the tree number is 

 preceded by the name of the orchard or an abbreviation indicating it. 



In the case of bearing trees it is most desirable to paint the number 

 on the tree trunk or on one of the main limbs. The figures should be 

 large and plain, so as to be readily identified from some distance. 

 Ordinary white-lead paint and a small brush are the materials used 

 for tree numbering. The numbers, when properly applied, have re- 

 mained in a satisfactory condition for six or seven years. Where it 

 is desirable to number small trees, the number may be stamped on a 

 metal tag, or painted on a wooden label, and attached to one of the 

 branches. The numbers should always be placed in the same relative 

 position on all of the trees, so that they can easily be found. 



