70 BULLETIN 815, U. S. DEPAETMENT OF AGEICULTURE. 



The object of these investigations has been to determine the 

 behavior of trees of the different strains and of the individual-tree 

 variations within the stram, to prevent the propagation of inferior 

 strains, to develop practical methods for eliminating undesirable 

 trees in established orchards, and to isolate and propagate the desir- 

 able strains and superior trees within these strains through bud 

 selection based on individual-tree performance records and inti- 

 mate tree knowledge. 



The plan of work as followed in these investigations has been to 

 secure individual-tree performance records in carefully selected 

 plats of the Lisbon variety. Each tree is picked separately, the 

 fruits assorted, counted, weighed, detailed notes taken, and other 

 data obtained, so that after a series of years definite conclusions con- 

 cerning strains and individual-tree behavior can be drawn. 



In these investigations five strains of the Lisbon lemon have been 

 studied, their characteristics described, and the performance records 

 of individual trees recorded. 



Some of the lessons taught by these studies include the discovery 

 of the importance of bud variations, the comparative value of the 

 different strains arising from them, the need of elimmating the un- 

 profitable strains and isolating the valuable ones through bud selec- 

 tion, and the origination and introduction of improved methods of 

 propagation for conserving and improving the production of the Lisbon 

 lemon variety. The desirable strains can be isolated by means of 

 careful bud selection based on individual-tree performance records 

 and intimate tree knowledge. 



Undesirable healthy trees or- inherently unproductive ones in 

 established orchards usually can be successfully top-worked by using 

 select fruit-bearing bud wood from performance-record trees. 



Undesirable unhealthy trees in old-established orchards can be 

 replaced with desirable younger trees which have been propagated 

 from selected fruit wood, provided proper attention is given to the 

 preparation of the planting hole and, later, to care in irrigation and 

 fertilization. 



Only fruit-bearing bud wood from superior parent trees which 

 have been selected on the basis of their performance records and 

 from intimate tree knowledge should be used for propagation or 

 for top-working. 



The California Fruit Growers' Exchange, a cooperative organiza- 

 tion of 8,000 citrus growers, has established a bud-supply department 

 as a result of these investigations. This department furnishes at 

 cost to growers and nurserymen bud wood from superior performance- 

 record trees. 



