BUD VARIATION IN THE LISBON LEMON. 3 
VARIABILITY WITHIN THE VARIETY. 
The systematic studies of the variations of the California citrus 
varieties were begun with the Washington Navel orange in 1909. 
Later, investigations were commenced with the Marsh grapefruit 
and Valencia orange. In June, 1911, the study of variations within 
the Eureka lemon variety was begun. This variety was found to be 
subject to variability in about the same degree as the citrus varieties 
previously studied.1 
One year after beginning the study of the Eureka lemon, tree- 
census studies were begun with the Lisbon variety. It was found 
that this variety was subject to variability in about the same degree 
as the Eureka. In order to secure definite information on this sub- 
ject individual-tree performance records were begun on a plat of 
trees of the Lisbon variety in June, 1913, included in which were 
typical trees of all the important strains discovered up to that time. 
In these studies detailed performance records have been obtained 
covering a total of 128 Lisbon lemon trees. The individual trees in 
these plats have been picked monthly as far as possible. As with the 
Eureka lemon studies, the frequent pickings during a period of several 
consecutive years have resulted in the accumulation of a very large 
mass of data and information, from which conclusions have been 
drawn as to strain and individual-tree characteristics. 
In addition to these detailed studies, cooperative individual-tree 
performance records have been carried on in several California lemon 
orchards during this period with about 13,000 trees of the Lisbon 
variety. 
The variability of the Lisbon lemon described in the discussion of 
the results of these studies must be clearly distinguished from the 
fluctuating variability due to climatic, soil, cultural, or other environ- 
mental influences. The variations considered in these studies are 
those which have been found to be transmitted by budding and are ~ 
inherent, variations. The fluctuating variations, such as modifica- 
tion of the size of the fruits, slight differences in the color of the 
leaves or fruits, or similar changes due to climatic conditions, cul- 
tural factors, or other causes, have not been taken into account 
except as indicating the effect of certain environmental factors in 
tree and fruit development. All of the variations considered in 
these studies have been traced to individual fruit or limb varia- 
tions in trees growing under normal conditions. 
OBJECTS OF THE INVESTIGATIONS. 
The objects of these investigations have been to determine the 
frequency and importance of bud variation in the Lisbon variety of 
lemon; to ascertain the relative value for commercial orcharding of 
1See U.S. Dept. of Agriculture Bul. 813, entitled ‘“ Citrus-Fruit Improvement: A Study of Bud Varia- 
tion in the Eureka Lemon.’’ 
