92 Ezvart and Rees .— Transpiration and the Ascent of 
quantity of eosin solution. However carefully the work is done a little air 
always enters, and by blocking some vessels might cause the liquid to rise 
more rapidly in the others than it does in the intact tree. 
Hence one tree, A, was sawn through with a cut sloping slightly 
downwards and an inch jet of water assured that no air entered. The sawn 
end was then cut afresh with a wood chisel under water and trimmed with 
a sharp razor. The second one, B, was cut with a sharp axe and the cut 
end exposed to air for thirty seconds, with the following results after each 
tree had been in eosin for two hours:— 
Height. Rate of ascent of eosin. Amount absorbed. Temperature. Condition. 
Tree A 3-65 metres 0-972 metre per hour 53-8 c.c. per hour 18-20° C. clear 
Tree B 5-30 metres 0-625 metre per hour 98-6 c.c. per hour 25-28° C. slightly cloudy 
It is evident, therefore, that any blocking with air lowers the rate 
of ascent of sap in the whole stem, and that the highest value obtained 
in any experiment will approach most closely to the rate of ascent in the 
intact tree. This is also shown by the fact that the rate of transpiration 
per sq. metre of leaf surface is always less under otherwise similar con¬ 
ditions from a cut tree with its base in water than from the intact rooted 
tree, and is still less when a cut branch is suspended in dry air. When 
transpiration is active the leaflets on a cut Acacia tree with its base in water 
begin to fold together in half an hour and are nearly or completely folded 
in two to three hours, while the leaves themselves droop downwards. 
Using every precaution and with a short exposure the maximum rate of 
ascent for a cut transpiring tree of Acacia was found to be 2*46 metres per 
hour, as in the following experiment. 
Acacia mollissima. 
Tree 3*8 metres high, lower branches close to ground removed. 
Cut under stream of water with sharp axe. 
Shade temp. 27° C. North wind. Time, 12-1 p.m. Dec. 7, 1908. 
Eosin ascended 2*46 metres in one hour. 
Amount absorbed, 552-8 c.c. per hour. 
Leaflets at angle of 30-90° at commencement. 
After half an hour angles began to lessen (deficiency of water?). 
At close of experiment distinct signs of drooping in main petioles. 
By noting the number of leaves and hence obtaining the transpiration 
rates per sq. metre from the cut tree and from a separated branch a control 
of the results can be obtained. Thus in a preliminary two-hour test with 
a two-year-old shoot of Eucalyptits cornuta 3 metres high, the eosin 
ascended 60 cm. per hour (shade temp. 19-21 0 C.) and the stem absorbed 
34 c-c. of water per hour. 
