4 BULLETIN 624, U. S. DEPARTMENT OF AGRICULTURE. 
viduals of the variety in one or more constant and recognizable 
characteristics and which are capable of perpetuation through vege- 
tative propagation. Within the various strains there are variations 
in the amount and commercial quality of the fruits produced by the 
individual trees. The variability of individual-tree production in 
the orchard as regards quantity, commercial quality, time of ripening, 
and other characteristics is of the highest importance to growers of 
fruit varieties. 
The variability of the trees and fruits within the variety is of 
fundamental significance from the standpoint of the grower and in 
any study of the conservation and stabilization of the variety as a 
whole. 
The Valencia strains are distinguished by differences in habits of 
growth, time of ripening fruits, quantity and quality of crops, and 
other definite and marked characteristics. The trees of certain 
strains were found to have upright habits of growth, while those of 
other strains are drooping or spreading. The trees of some of the 
strains produce, as a rule, full crops of the best-grade fruit, while 
those of other strains produce light crops of low-grade fruit. The 
trees of at least one of the strains produce early-ripening crops, 
while those of other strains produce later ripening fruits. The leaves 
of the trees of some of the strains are large, broad, and bluntly 
rounded hi shape, while trees of other strains have small, narrow, and 
sharply pointed leaves. 
In many cases, fruits of two or more of the different strains have 
been found on the same tree grown from a single bad and therefore 
upon the same individual stock. Such instances have shown the 
fallacy of the theory that the different strains are variations due to 
climatic or soil conditions or the influence of different stock. Later, it 
was found that the different strains occurring in a single tree could be 
isolated through bud selection hi propagation, thus proving that the 
differences observed were true inherent cases of bud variation. 
The mixture of strains in the Valencia orchards under observation 
was found to be so marked and frequent as to warrant careful inves- 
tigations of their relative value. The results of these investigations, 
which have covered more than four years, together with suggestions for 
the isolation of the best strains of this variety through bud selection 
and for the stabilization of the variety through the propagation of 
only the most desirable strains, are set forth in the following pages. 
OCCURRENCE AND FREQUENCY OF BUD VARIATIONS. 
A casual observation of the Valencia orange trees selected for 
these investigations will reveal little of the startling condition of bud 
variability existing in the trees and their fruits. Several Valencia 
orange growers, with many years of experience in the culture of this 
