1911] OV ERTON—TRANSPIRATION AND SAP-FLOW 37 
cells in such an experiment, owing to its retention in the walls 
of the wood vessels and its inability to diffuse well laterally. In an 
experiment in which the base of the trunk was first placed for 2 days 
in formic aldehyde, after which eosin was added to the solution, 
the latter rose to the top in 4 days. Ewart finds, however, that 
in this case eosin rises not in the poisoned part of the wood, that is, 
the outer younger rings, but in parts which the formalin had not 
penetrated at all or only in very dilute form and which were still 
alive. Even in this case the flow of eosin solution was only tempo- 
rary, nearly all conductivity being practically lost in 5 days. Ewart 
concludes that his results apparently show that eosin solution fol- 
lowing formalin instead of rising in the young poisoned portion 
of the wood passed upward through the unkilled parts. ‘The 
ascent of sap in trees must be regarded as a vital problem in which 
vital actions, directly or indirectly, take part,’’ and is ‘“‘a vital 
problem in so far as it depends upon conditions which hitherto 
can only be maintained in living wood.” 
REINDERS (23) found that manometers placed one above the 
other on the same stem behave quite independently of one another, 
sometimes one-and sometimes another showing the lower pressure. 
In a suspended water column the pressure decreases gradually 
toward the top. On account of the differences of pressure observed 
in Sorbus latifolia, Cornus, and Syringa, REINDERS feels constrained 
to conclude that the living wood is normally able to pump water 
actively. The irregularities in his pressure measurements led him 
to seek for the cause in the activity of the living cells of the wood. 
He believes that the irregularities would disappear if these influ- 
ences were removed; therefore he killed with steam a 2 m. stem of 
Cornus in two places for a distance of 10-12 cm., the distance 
between the killed portions being 66 cm. He also killed a 2.5 m. 
branch of Sorbus throughout its length, observing that the manom- 
eters at once showed more regularity; the leaves on this stem 
remained uninjured for 3 weeks. Four manometers were attached 
to the stem of a 2 m. Syringa vulgaris bush; the instruments after 
a short period all showed an equal ‘“‘suction,”’ which soon varied 
during the night and day, although the differences in pressure 
were small, a higher pressure sometimes being indicated in one and 
