UNITED STATES DEPARTMENT OF AGRICULTURE 
^?*Wd. 
BULLETIN No. 624 
Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 
Washington. D. C. 
PROFESSIONAL PAPER 
July 25, 1918 
CITRUS-FRUIT IMPROVEMENT: A STUDY OF BUD 
VARIATION IN THE VALENCIA ORANGE. 1 
By A. D. Shamel, Physiologist in Charge, L. B. Scott, Pomologist, and C. S. 
Pomeroy, Assistant Pomologist, Fruit- Improvement Investigations, Office of Hor- 
ticultural and Pomological Investigations. 
CONTENTS. 
Page. 
California citrus varieties 
History of the Valencia 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 variations of fruits 
Page. 
Minor variations of fruits 13 
Lessons taught by these investigations 13 
Presentation of data 14 
Comparative value of the strains 114 
The unintentional propagation of undesirable 
strains 115 
The isolation of strains through bud selection 116 
Top-working undesirable trees 118 
Summarv 119 
CALIFORNIA CITRUS VARIETIES. 
The commercially important varieties of citrus fruits grown in 
California are the Washington Navel, the Valencia, and the Mediter- 
ranean (Mediterranean Sweet) oranges; the Dancy tangerine; the 
Eureka and Lisbon lemons; and the Marsh (Marsh Seedless) grape- 
fruit. Other less important varieties grown only to a limited extent 
include the St. Michael, Navelencia, Ruby blood, and Malta blood 
oranges, and the Villafranca lemon. Of the two leading orange 
varieties the Washington Navel is by far the most widely cultivated, 
producing an annual crop of about 27,000 carloads of fruit. 2 This 
variety ripens its fruit from November to June, inclusive. The 
Valencia ripens its fruit from June to October, inclusive, and produces 
1 This is the second in a series of publications summarizing the citrus-fruit improvement investigations of 
the Department of Agriculture. The first report of this character was presented in the following publica- 
tion: Shamel, A. D., Scott, L. B., and Pomeroy, C S. Citrus-fruit improvement: A study of bud varia- 
tion in the Washington Navel orange. U. S. Dept. Agr. Bui. 623, 146 p., 16 figs., 19 pi. 1918. In that 
bulletin the methods of conducting the investigational work are described more in detail than in the pres- 
ent publication. 
2 Wallschlaeger, F. 0. The world's production and commerce in citrus fruits and their by-products. 
Citrus Prot. League, Cal., Bui. 11, p. 70. 1914. 
14648°— IS— Bull. 624 1 
