9 2 
Journal of Agricultural Research 
Vol. XXI, No. i 
Table IV .—Mean and root-mean-square deviations of sap concentration in apical and 
basal regions of apricot shoots 
Part of shoot. 
Mean sap 
concentra¬ 
tion. 
Root -mean- 
square de¬ 
viation. 
Stp'tn jvniral . 
A imospheres. 
15-83 
59 
19- 59 
18.93 
Atmospheres. 
2. 06 
Stem, basal . 
2 . 77 
I. 74 
Leaves, apical . 
Leaves, basal. 
1. 68 
The mean sap concentrations, shown in Table IV, bear out the facts 
represented by the graphs. The sap concentration at the apical end 
of the shoot was higher in both stem and leaf, although there is very 
little difference in the leaves at the opposite ends of the shoot. 
The root-mean-square deviations show that the sap concentration of 
the stem had a greater tendency to fluctuate about its mean value than 
that of the leaf. This may be taken to indicate that the sap concentra¬ 
tion of the leaves tends to maintain an equilibrium which is not easily 
disturbed by fluctuations in the environment. The variation in the sap 
concentrations of the leaves from the middle of July on to the end of 
the season is within the range of experimental error. Other investi¬ 
gators have found that the young leaves on a plant had a lower sap con¬ 
centration than the older leaves. A similar condition may exist in the 
apricot tree, but it would require that one should carefully select the 
leaves in order to demonstrate it. At the time the foregoing determina¬ 
tions were begun on the apricots, the shoots had made two-thirds of 
their growth for that season. 
It thus appears that there is a gradual increase in concentration of 
sap from the base to the apex of a growing shoot. 
There is, in some quarters, a belief that the apical leaves on young 
shoots are meagerly supplied with solutes and that the practice of remov¬ 
ing the terminal half of the young shoots is justifiable at any time after 
mid-summer. The determinations made upon these apricot shoots 
seem to speak against such a belief. From the middle of the summer to 
the first of December there was little real difference in the sap concen¬ 
tration of the leaves at opposite ends of the new shoots. 
The existence of a gradient in the sap concentration of apricot shoots 
was shown by determinations made on June io, 1920, using a sample of 
young shoots having an approximate length of 120 cm. The leaves were 
removed and the stems were cut into four lengths of 30 cm. each. The 
sets were designated as A, B, C, and D. A designated the apical set 
of cuttings and D the basal set. 
