4 BULLETIN 815, TJ. S. DEPAETMENT OF AGEICULTURE. 



the various strains originating from bud variations; k^ discv'Vfir 

 methods for isolating the best and eliminating the inferior strains 

 through bud selection; to originate and introduce methods for 

 replacing trees of inferior strains in established oi-chards through 

 tojD-working or replanting; to introduce methods for securing reliable 

 supplies of buds from superior performance-record trees for use by 

 propagators; and to establish a system of individual-tree record 

 keej^ing in commercial lemon orchards, in order to locate the desirable 

 and undesirable trees. 



PLAN OF THE INVESTIGATIONS. 



These investigations have been carried on by means of individual- 

 tree performance records, as in the case of the citrus varieties pre- 

 viously studied. The term '^ performance record" is used to mean 

 a systematic record for a period of several years of the yield and 

 behavior of individual trees. This record includes notes of the 

 amount, the commercial quality, and the variability and other 

 important characteristics of the fruits produced by the individual 

 trees. In the case of lemon trees, individual performance records 

 for at least two consecutive and normal seasons on trees which have 

 reached a full bearing age are considered necessary in order to 

 determine the value of the trees for commercial fruit production. 

 Similar records for at least four years are advisable, in order to fur- 

 nish the basis for the selection of superior trees as sources of bud 

 wood for propagation. 



The same general methods of picking, handling, assorting, weigh- 

 ing, counting, and classifying the fruits that were described in detail 

 in United States Department of Agriculture Bulletin 813, entitled 

 "Citrus-Fruit Improvement: A Study of Bud Variation in the Eureka 

 Lemon," were followed in the studies of the Lisbon lemon. 



The conditions considered essential in the location of the Lisbon 

 individual-tree performance-record plats were the same as those 

 which determined the final location of similar record plats of other 

 varieties, namely, (1) the production of successful and profitable 

 crops of fruit; (2) location on virgin land in order to avoid any in- 

 fluence of previous cultural treatment; (3) protection from cold, 

 strong winds, or other climatic causes of tree and fruit injuries ; (4) 

 the absence of radical pruning, rebudding, top-working, or other 

 similar tree treatments; (5) freedom from or the effective control of 

 diseases and insect pests; (6) uniform irrigation and cultural practices 

 during the entire history of the orchard ; (7) reliable information con- 

 cerning the history of the buds used in the propagation of the trees 

 and the kind of stocks; (8) the prospect of settled ownership for a 

 period of years ; and (9) the absence of apparent local environmental 

 factors influencing tree behavior, so that the results of the individual- 

 tree studies would be truly comparative. 



