16 BULLETIN 623, U. S. DEPARTMENT OE AGRICULTURE. 
usually is small, frequently rudimentary, with no development 
except in the rind. 
The Washington is the most valuable of all the Washington 
Navel orange strains on account of the high productiveness of the 
trees and the superior commercial quality of the fruit. The com- 
mercial characteristics of the oranges of this strain are not equalled 
in value by those of any other navel orange grown in California at 
the present time. 
THOMSON STRAIN. 
The Thomson strain, frequently called the Washington Improved 
or the Thomson Improved, has been extensively propagated com- 
mercially and is generally recognized in California as an established 
P545A-HH 
Fig. 5. — A typical tree of the Australian strain of the Washington Navel orange (at the left) in comparison 
with a typical tree of the Washington strain (at the right). 
variety. 1 Trees, individual fruits, and limbs bearing several fruits 
of this strain frequently are found in orchards of trees of the Wash- 
ington strain, showing that it is a common bud variation. The trees 
show an unusual degree of variability in the character of their fruits, 
one tree frequently bearing several distinct strains. The established 
orchards of this strain show tree and fruit variations to such an 
extent that this condition is recognized as distinctly detrimental to 
its commercial value. Most of the Thomson trees in the investiga- 
tional performance-record plats have produced one or more fruits 
1 In the Yearbook of the U. S. Department of Agriculture for 1911, pp. 436-438, the history and a com- 
plete description of this strain are presented by Dr. Wm. A. Taylor. At the time of the preparation of this 
paper it was thought by most growers that the Thomson orange was an established variety of independent 
origin from the Washington Navel orange. These investigations have shown that it is but a strain of the 
Washington Navel orange. 
