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UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 623 
Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 
Washington, D. C. 
PROFESSIONAL PAPER 
July 22, 1918 
CITRUS-FRUIT IMPROVEMENT 
A STUDY OF BUD VARIATION IN THE 
WASHINGTON NAVEL ORANGE 
By 
A. D. SHAMEL, Physiologist in Charge, L. B. SCOTT, Pomologist, and 
C. S. POMEROY, Assistant Pomologist, Fruit-Improvement Investigations, 
Office of Horticultural and Pomological Investigations 
CONTENTS 
Introduction 1 
History of the Washington Navel Variety 2 
Variability within the Variety 3 
Occurrence and Frequency of Bud Varia- 
tions 5 
Objects of the Investigations 7 
Plan of the Investigations 7 
Methods of Keeping Performance 
Records 9 
Descriptions of Some of the Important 
Strains 14 
Page 
Individual Fruit Variations 24 
Minor Variations of Fruits 27 
Lessons Taught by These Investigations 27 
Presentation of Data 29 
Comparative Value of the Strains . . . 140 
The Unintentional Propagation of Unde- 
sirable Strains 141 
The Isolation of Strains through Bud 
Selection 142 
Top- Working Undesirable Trees . . . 144 
Summary 145 
WASHINGTON 
GOVERNMENT PRINTING OFFICE 
1918 
