118 
AMERICAN JOURNAL OF BOTANY 
[Vol. io, 
In making the tests for acidity and water content, the lemons were cut 
once longitudinally and once transversely, thus dividing them as nearly 
as possible into 4 equal parts. One half of each end was used for the acidity 
test and the other half to determine the water content. This was done to 
determine whether or not there were any differences between the acidities 
and water contents of the two ends of the lemon. In determining the acidity 
the fleshy pulp alone of the fruit was used, but both pulp and peel were used 
in determining the water content. 
The hydrogen electrode was used to determine the acidity. The pulp 
to be tested was cut free from the peel and ground in a mortar, and the 
juice was extracted in a tincture press. In making the water-content 
determinations the peel and pulp were finely cut, placed in weighing bottles, 
and dried to constant weight in a vacuum oven. 
In connection with the determinations of acidity of lemons at different 
stages of growth, other tests were made to determine the acidity of mature 
lemons taken from the packing houses or directly from the trees. A series 
of experiments also was performed to determine whether or not the leaves 
of the lemon trees may be an active factor in drawing water from the fruits. 
Results and Discussion 
Growth Rate and Water Content of Lemons 
The subjects of growth rate and water content are so closely related 
that no attempt will be made to discuss them separately. 
The Eureka lemon tree is one which, under conditions of comparatively 
high humidity and low temperature, such as prevail near the coast in south¬ 
ern California, produces new fruit in practically every month of the year. 
Farther inland, where the humidity is lower and the temperature higher, 
there is a more marked tendency toward seasonal production. In this 
respect, fruit production apparently is influenced also by the age of the tree, 
because the older the tree the greater tendency it shows toward seasonal 
rather than continuous production. Evidence of this latter condition 
was shown in the three groves chosen in which to carry on this work. It 
was found that no fruits were set during the month of September at River¬ 
side where the trees were 6 years old; none during September and March 
at Corona where the trees were 20 years old; and none during August, 
September, October, and March at Upland where the trees were 30 years 
old. 
It was found also that, although there is a tendency toward continuous 
production of fruits, many more are produced during the spring set of 
fruit than at any other time of the year. This agrees with the findings of 
Reed (6) in his study of the relation between the flowers and the fruits of 
the lemon. He found that approximately 66 percent of the fruit buds 
appear during March and April, 17 percent from May to October inclu- 
