304 BOTANICAL GAZETTE [ MARCH 
tional to the absolute temperature, were unsuccessful, the turgor being tvo high 
at low temperatures. In investigating the influence of temperature on the 
rapidity of the osmotic movement of water more satisfactory results were 
obtained. It was found, for instance, that if cylinders of the pith of Sambu- 
cus 580.5"™ long were placed in a 24 per cent. cane sugar solution at oto 1°C., 
and at 20°C., the contraction in 2" 15™was to 176.5™™ in the former, to 147" 
in the latter; that is, at 20° more that eight times as much water had been 
given off as at zero, transverse contraction being neglected. Conversely, when 
pith was placed in distilled water at 4° and at 26°C., the elongation within 15™ 
was about four times as great in the latter as in the former. In experiments 
with roots (Vicia Faba and Phaseolus multifiorus) the difference was less, the 
ratio never exceeding 1 to 2.5 during the first five minutes, and decreasing with 
the duration of the experiment. The ratio of the amount of elongation of 
plasmolysed roots in distilled water at 4° and 26°C. was about 1 to 3 during the 
first ten minutes. Poiseuille’s formula provides for an average increase in 
the viscosity of water of 0.034 for each degree C. above zero. Pfeffer’s obser- 
vations at 7.1°, 17.6’, and 32.5°C. suggest an increased rapidity of osmosis 
through copper-ferrocyanide membranes of 0.045 per degree, or from I to 1.9 
with 20° increase. His own figures being considerably higher, Krabbe con- 
cludes that they must depend on the living nature of the protoplasm. At a 
low temperature, the condensation of the protoplasm makes it so resistent to 
the passage of water that if pith cylinders in ice water, whose elongation has 
ceased, be split, the halves become concave on the inner surface. In a cert- 
tain sense the condition of the protoplasm here regulates the turgor without 
being pervious to anything but water.** Krabbe believes that at 24°C. 
the intermicellar openings are already large enough to permit some eX0s- 
mosis of the cell content into pure water, but no figures are given in proof. 
_ The increased inner friction of water when cooled, represented by Poi- 
seuille’s: formula, ‘may claim more or less of a share in the decreased rapidity 
osmosis, as it is slightly or decidedly overshadowed by friction against the 
‘membrane. _ But the latter element is always present, and when 50 to 200 
membranes obstruct the way it may well suffice to explain the difference of 
tensions at surface es interior ee the pith cylinders. It is no more reason- 
able to ‘expect | Liff | to show like variation in this respect than 
to assume ‘for all substances a common coefficient of expansion when heated. 
The resistance — is an unknown®% function of the diameter of the 
interstices. The f fi er th e already Roche me greater saiaies be the effect of a 
pean to 
aur Sea ee gece Se ain res ake a 
pee it + eich ™ 
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t und der Vacuolen, etc. at 156} 
roc Be nt 6h fourth power 
