6 BULLETIN 813, U. S. DEPARTMENT OF AGRICULTURE. 



In these studies detailed performance records have been obtained 

 on a total of 252 Eureka^ lemon trees in the investigational plats. 

 The individual trees in these plats have been picked monthly as far as 

 possible. The frequent pickings and the resulting large amount of 

 detailed work in assorting, classifying, counting, weighing, and 

 recording the yields has made it necessary to limit to a comparatively 

 small number the trees selected for individual-tree performance- 

 record studies. The many pickings during a period of several con- 

 secutive years have resulted in the accumulation of a very large mass 

 of data and information, from which conclusions have been drawn as 

 to varietal, strain, and individual-tree characteristics. 



In addition to these detailed studies, cooperative individual-tree 

 performance records have been carried on in several California lemon 

 orchards during this period with about 14,000 trees of the Eureka 

 variety. 



The variability of the Eureka lemon described in the discussion 

 of the results of these studies, due to bud variations, must be clearly 

 distinguished from the fluctuating variability due to climatic, soil, 

 cultural, or other environmental influences. The variations con- 

 sidered in these studies are those which have been found to be in- 

 herent and transmitted by budding. The fluctuating variations, 

 such as modifications of the size of the fruits, slight differences in the 

 color of the leaves or fruits, and similar changes due to climatic con- 

 ditions, cultural factors, or other causes, have not been taken into 

 account except as indicating the effect of certain environmental 

 factors in tree and fruit development. All of the variations considered 

 in these studies have been traced to individual fruit or limb variations 

 in trees growing under normal conditions. 



OBJECTS OF THE INVESTIGATIONS. 



The objects of these investigations have been to determine the 

 frequency and importance of bud variations in lemon trees of the 

 Eureka variety; to ascertain the relative value for commercial or- 

 charding of the various strains originating from bud variations; to 

 discover 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 orchards through 

 top-working or replanting; to introduce methods for obtaining relia- 

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

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

 keeping in commercial lemon orchards, in order to locate the desir- 

 able and undesirable trees. 



1 A report on variations in the Lisbon variety will be found in Department of Agriculture Bulletin No. 

 815, entitled " Citrus-Fruit Improvement: A Study of Bud Variation in the Lisbon Lemon." 



