INTERNAL DECLINE OF LEMONS 
II. GROWTH RATE, WATER CONTENT, AND ACIDITY OF 
LEMONS AT DIFFERENT STAGES OF MATURITY 1 
E. T. Bartholomew 
(Received for publication April 12, 1922) 
This work was undertaken to determine the possible bearing on the 
etiology of internal decline of lemons 2 of ( a ) the rate at which lemons in¬ 
crease in size as influenced by climatic and seasonal changes and by the 
time of year at which the fruit is set, and ( b ) the increase in acidity and water 
content of the fruits at different stages in their development. 
Statements have been made by different writers concerning the acidity 
and water content of mature lemons but not of lemons at different stages 
of maturity. Wehmer (8) gives the water content of mature lemons as 
82.64 percent,, a figure which is too low, at least for California lemons, as 
is indicated later in this discussion. Clark and Lubs (2) give a pH value 
of 2.2 for the true acidity of juice from mature lemons. The results ob¬ 
tained in this work agree very well with that figure. 
Methods of Experimentation 
Groves located at Corona, Upland, and Riverside were chosen as suit¬ 
able places in which to carry on the work. These groves are all of different 
ages, as follows: at Riverside, 6 years; at Corona, 20years; and at Upland, 
30 years. All three groves are Eurekas, the variety usually grown in 
California. 
The sizes of the lemons were determined by diameter measurements 
with a vernier caliper. In each of the three groves 200 small lemons were 
measured and tagged each month for one year. When a new lot was meas¬ 
ured and tagged, those previously tagged and measured were remeasured, 
so that each lemon was measured each month until it dropped from the 
tree or until it came to maturity and was picked. Fruits were tagged on 
a chosen group of trees and in many different locations on each tree. Fruits 
averaging from 0.44 to 1.29 cm. in diameter were chosen for the initial 
measuring and tagging. Fruits of these sizes are about 1 to 2 months old, 
depending upon the season and other conditions attending their growth. 
Each month, following the month of initial measuring and tagging, samples 
were brought to the laboratory and tested for acidity and water content. 
1 Paper no. 95, University of California Graduate School of Tropical Agriculture 
and Citrus Experiment Station, Riverside, California. 
2 For a description of the abnormality known as internal decline of lemons, the reader 
is referred to the first article in this series by Bartholomew, Barrett, and Fawcett (1). 
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