UNITED STATES DEPARTMENT OF AGRICULTURE 
i BULLETIN No. 623 fL 
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 
History of the Washington Navel variety — 
Variability within the variety 
Occurrence and frequency of bud variations. 
Objects of the investigations 
Plan of the investigations 
Methods of keeping performance records 
Descriptions of some of the important strains. 
Individual fruit variations 
Page. 
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 undesirable 
strains 141 
The isolation of strains through bud selection . 142 
Top-working undesirable trees 144 
Summary 145 
INTRODUCTION. 
The Washington Navel orange is the most important citrus variety 
grown in California. The total orange crop of the State, based upon 
the shipments of a normal year, is about 39,500 carloads, of which 
approximately 27,000 cars are of the Washington Navel variety. 1 
In the report of the general manager of the California Fruit Growers' 
Exchange for the year ended August 31, 1916, it is stated that a 
total of 37,229 cars of oranges and grapefruit was shipped from 
California during that period. The grapefruit crop amounted to 
about 300 cars. It is also stated in this report that the California 
Valencia orange crop of the year under discussion would amount 
to between 13,000 and 14,000 carloads. No mention is made of the 
size of the crops of the Mission Sweet Seedling, Mediterranean Sweet, 
St. Michaels, Bloods, and other varieties, which are now grown to 
only a very limited extent in California, probably not to exceed 1,500 
1 Wallschlaeger, F. O. The world's production and commerce in citrus fruits and their by-products. 
Citrus Prot. League, Cal., Bui. 11, p. 70. 1914. 
14575°— 17— Bull. 623 1 
