320 
Journal of Agricultural Research 
Vol. XXVI, No. ? 
sour orange stocks and the trees were grown in cooperation with the 
Citrus Experiment Station of the University of California. In July, 
1917, a part of the progeny trees grown from these propagations were 
planted on the Station grounds at Riverside, Calif. 
The behavior of the progenies as a whole offers most striking and con¬ 
clusive proof of the value and importance of bud selection in citrus 
propagation and the wisdom of the methods which have been almost 
universally adopted in commercial propagation in the Southwest in 
selecting budwood from uniformly productive and superior parent trees. 
THE UNPRODUCTIVE STRAIN OF THE WASHINGTON NAVEL ORANGE 
The unproductive strain of the Washington navel orange is one of the 
most important both from the commercial and scientific standpoints. 
A typical example of the occurrence of an unproductive limb variation 
was found in 1910 in a tree grown from a single bud of the Thomson 
strain of the Washington navel orange in an orchard planted in 1903 
near the home of the senior writer at Riverside, and this tree has been 
under observation each year since its discovery. 
This unproductive limb forms the upper part of the main branch of the 
tree, constituting about one-half of the growth of the tree. It was 
mentioned on page 25 of the United States Department of Agriculture 
Bulletin 623, 3 entitled, “Citrus-Fruit Improvement: A Study of Bud 
Variation in the Washington Navel Orange/’ and was illustrated in 
figures 7 and 8 of that publication. Figure 7 is a general view of the 
tree as it appeared in the summer of 1914, and is reproduced herewith 
as Plate 1; figure 8 shows the framework structure of the tree with the 
unproductive limb marked with a handkerchief. The orchard in which 
this tree stands is favorably located, has been given good cultural care, 
and the tree has never suffered from frost injury, insect attacks, or 
fungus diseases. The leaves of the unproductive limb are somewhat 
different from those of the normal branches, being characteristically 
smaller, more sharply pointed, more yellowish-green in color, and less 
abundant. There are no apparent differences in the time of blooming or 
in the number or structure of the flowers borne by the different branches 
of the tree. 
Detailed performance records of this tree were not secured on account 
of the fact that it was located at some distance from the Washington 
navel orange performance-record plats and lack of time and assistance 
made it impracticable to obtain yield data from it, as was the case with 
many other interesting isolated trees wdiich have been closely observed 
for a number of years. The yearly observations of the behavior of this 
tree both before and after propagations were made from it have shown 
that the unproductive limb has been consistently unproductive or barren, 
never having produced more than six fruits in any year until the present 
season, while the remainder of the tree has borne normal crops. Whenever 
fruits have been produced on the unproductive limb they have been 
typical Thomson oranges like those borne by the normal branches of the 
tree. Some of them have shown minor variations in markings of the rind, 
as is more or less characteristic of the fruits from the other branches of the 
tree and of the variety a£a whole. For the present season, 1922-23, the 
normal branches of this tree are bearing approximately 200 fruits, while 
* Shamel, A. D., Scott, I,. B., and Pomeroy, C. S. citrus-fruit improvement: a study of bud 
VARIATION IN THE WASHINGTON NAVEL ORANGE. U. S. Dept. Agr. Bui. 623, p. 25, fig. 7-8. 1918. 
