OSMOTIC CONCENTRATION OF LEAF SAP 277 
of an increase in the concentration of the leaf sap with increase 
in height of insertion could hardly be desired! 
On the assumption of the adjustment of the leaf cells to an 
increased load—an assumption which we are not at this moment 
either urging or combating—the increase in osmotic concentra- 
tion of the sap of the tissues collected at a higher level, L, over 
that of tissues collected at a lower level, Lo, should be proportional 
to the combined weight of two factors: (a) the hydrostatic head, 
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DIAGRAM I 
