The Rise of Sap in a Tropical Liana.

It was discovered in a Palestine orchard that citrus trees do not necessarily wilt when the trunk is cut from opposite sides at different levels so that every vessel is severed (2). Similar observations have been made on several other species Qf trees (3). Furthermore, it is known that every transpiration column throughout the cross section of a tall grapevine can be broken by air, without retarding the water uptake. When the air breaks are too extensive the transpiration slows down considerably, but it still may be sufficient to prevent wilting or even to permit a wilting plant to recover (4). It is common to these cases that air breaks existed in all or most of the active vessels throughout a full cross section of the stem, so that the transpiration stream for some distance, at least, must have run only through the interstices between the vessels. These phenomena have an important bearing on the cohesion theory, as well as on the relation between vascular and interstitial sap flow in the stem, and it has been our endeavor in the present investigation to elucidate the situation by experimental studies of hydrodynamic conditions in a liana.