1911] OVERTON—TRANSPIRATION AND SAP-FLOW 10g 
being kept in connection with the roots remain for a considerable 
period turgescent, but sooner or later wither and die. This is 
very distinctly shown in table IV, from which data it was concluded 
that the leaves above a steamed portion never remained longer than 
18 days without withering. This was shown to be true when only 
5 cm. of the stem were steamed, while the leaves remain turgid 
for 3 days only when 30 cm. were killed. It has been shown that 
in Cyperus sufficient water to maintain the turgidity of the leaves 
for 3-18 days will rise through a stem 15-60 cm. high with a section 
5-30 cm. long, which has been killed by steam. It has also been 
shown that sufficient water to keep the leaves turgescent for 3 
months can ascend through a stem 23 cm. high when 1o cm. are 
killed with CuSO,. It follows from my observations that the leaves 
wither above a longer heated stretch faster than above a shorter one, 
as has been observed by JANSE, URSPRUNG, Drxon, and ROSHARDT. 
It is further evident that when short portions of the stems are 
steamed (5-10 cm.), the leaves above do not wither quite as quickly 
as those on stems cut from the same plant and placed in water 
under the same conditions of light, temperature, and air moisture. 
Leaves cut and not placed in water always lose their turgidity and 
dry long before those on steamed stems, regardless of the length 
of the killed portion. Such cut branches lose their turgidity in 
1-2 hours, and become completely dry in 24-48 hours. The fact 
that the leaves on heated stems remain longer turgid than those 
cut and left in air shows that a certain amount of water passes 
through the killed portion, as is also admitted by Ursprunc. This 
is also clearly shown in a quantitative way, by comparing the 
transpiration after killing a certain portion of the stem with steam 
with that before the steam was applied. Such a comparison is 
brought out in tables V and VI. The amount of water passing 
through such a steamed stem rapidly diminishes, falling off almost 
immediately from 80 per cent to 50 per cent of the dry weight 
of the leaves, until the leaves become air dry, when they still 
contain about 11 per cent of the dry weight of water. 
Ursprune’s conclusion from such experiments, that living cells 
are necessary for sap-flow, is certainly not obviously necessary. 
* 
The long period during which the leaves remain turgid in his own 
