94 
Journal of Agricultural Research 
Vol. XXI, No. I 
fluctuation during the period of the observations than that of the shoots. 
In all cases these leaves were not more than i year old and were perform¬ 
ing the functions common to orange leaves of their age. It seems diffi¬ 
cult to escape the conclusion that in some way the concentration of 
solutes in the leaves tends to reach and maintain an equilibrium, and 
that this equilibration occurs regardless of the variations in concentra¬ 
tion which simultaneously take place in the adjacent shoots. 
CONCENTRATION OF THE SAP IN VARIOUS LAYERS OF THE APRICOT 
SHOOTS 
The following osmotic pressures were found in a sample collected on 
June 27: mature leaves, 17.12 atmospheres; cortical layers of the stem, 
13.82 atmospheres; woody, subcortical layers, 10.21 atmospheres. 
These figures indicate that the sap of the wood is less concentrated than 
that of the leaves and are in entire agreement with those previously 
obtained. They show quite remarkable differences in the sap concen¬ 
tration of the different layers of the stem. The cortical layers (including 
the phloem) undoubtedly owe their higher concentration to their content 
of plastic organic substances. Although subject to variation, these 
relations might be expected to hold throughout the season. 
SAP CONCENTRATION OF THE APRICOT TREE AFTER GROWTH 
CEASES 
It is well known that during the progress of "ripening” the woody 
tissues are the seat of changes involving the translocation and deposi¬ 
tion of many kinds of compounds. A series of determinations was made 
after the shoots on these trees ceased to show further elongation to see 
whether there were appreciable changes in sap concentration in the early 
part of the dormant period. 
TABLE V .—Sap concentration of apircot shoots during fall and early winter 
Date. 
Osmotic pressure. 
Unpruned 
trees. 
Heavily 
pruned 
trees. 
Oct. 23. 
A tmospheres. 
18. 60 
19. IO 
19. OO 
16.33 
19. IO 
15 - 85 
Atmospheres. 
15. 81 
I 7 * 9 ° 
17. 20 
17. 22 
22.30 
18.7s 
Nov. 6. 
20. 
Dec. 4. 
18. 
Tan. 20. 
j y . 
These figures show that there are appreciable changes in the concen¬ 
tration of the sap even though no active growth is taking place. The 
changes may, however, be referred in part to changes in the amount of 
