UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 813 
Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 
Washington, D.C. 
PROFESSIONAL PAPER 
June 25, 1920 
CITRUS-FRUIT IMPROVEMENT: A STUDY OF BUD 
VARIATION IN THE EUREKA LEMON. 1 
By A. D. Shamel, Physiologist, L. B. Scott, Pomologist, C. S. Pomeroy, Assistant 
Pomologist. and C. L. Dyer, Scientific Assistant, Fruit-Improvement Investiga- 
tions, Office of Horticultural and Pomological Investigations. 
CONTENTS. 
Importance of the lemon industry 1 
History of the Eureka variety 3 
Variability within the variet y 3 
Objects of the investigations 6 
Plan of the investigations 7 
Methods of keeping performance records 8 
Tree numbers 8 
Picking 9 
Assorting 9 
Recording the data 11 
Descriptions of the important strains 13 
Eureka strain 13 
Small-Open strain 15 
Shade-Tree strain 16 
Dense-Unproductive strain 19 
Pear-Shape strain 20 
Page. 
Descriptions of the important strains — Contd. 
Dense-Productive strain 21 
Variegated strain 21 
Sporting strain 22 
Lessons taught by these investigations 23 
Presentation of data 25 
Comparative value of the strains 78 
The unintentional propagation of undesirable 
strains 79 
The isolation of strains through bud selection. 80 
Top-working undesirable trees 81 
Replacing undesirable trees in bearing or- 
chards 84 
The selection and care of bud wood 85 
Summary 87 
IMPORTANCE OF THE LEMON INDUSTRY. 
The lemon {Citrus limonia Osbeck), as grown in the United States, 
is largely a California product. According to the Thirteenth Census 
of the United States there were 957,000 lemon trees of bearing age 
in the United States in 1910 and 396 7 000 under bearing age, of which 
941,293 and 379,676, respectively, were in California. The total 
production of all States in 1909 was reported as amounting to 
2,770,313 boxes, of which California produced 2,756,221 boxes. 
1 This is the fourth in a series of bulletins summarizing the citrus fruit-improvement investigations of the 
Department of Agriculture. The three former reports, IT. S. Dept. Agr. Buls. 623, 624, and 697, presented 
the results of studies with the AVashington Navel orange, the Valencia orange, and the Marsh grapefruit, 
respectively. A report on bud variations in the Lisbon lemon will be found in U. S. Department of Agri- 
culture Bulletin 815, entitled "Citrus-Fruit Improvement: A Study of Bud Variation in the Lisbon 
Lemon." 
135336°— 20— Bull. 813 1 
