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3. The assimilation under different intensities of light.
The experiments in the influence of the light with normal CO,
percentage (0.57 mg. per litre of air) fully confirm earlier obser
vations. In tables I, IV, VIII, IX, X, and XII are included series
of experiments with Nasturtium palustre, Alriplex latifolium, Stellaria
nemorum, Oxalis Acetosella, Melandrium rubrum, Circea alpina. I
found that the sun-plants (Nasturtium and Atriplea) followed a more
uniformly bent curve than the shade-plants examined. For the
latter the curve showed a sharp bend at a certain quite low intensity
of light, and then passed over into a line parallel with the abscissa.
BoYSEN-JENSEN’S curves (1918) for a number of sun- and shade.
plants present a similar appearance lo mine. BoysEN-JENSEN has
however collected the results from four shade-plants and shade-
forms respectively in a single skeleton curve (1918, p. 348), which
1 et
a
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|
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nz ZE grae | | Metandrium
teltaria-
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Bell dor leh Pen
lau dia A ee
oy
Fig. 2. Diagram showing the influence of different intensities of light upon the
CO, assimilation of certain shade-plants. The curve of Circea is almost identical
with that of Melandrium and therefore was not drawn.
can therefore have no pretensions to accuracy. The values which
he obtains for the Oxalis Acetosella also examined by me vary
extremely, and the horizontal part of the curve is considerably
lower than is indicated by my values. While BOYSEN-JENSEN
describes an optimal CO, absorption of only 0.9 mg. per 50 cm.*
per hour, I have found under similar conditions a CO, absorption
of 2.4 mg. Probably BovsEN-JENSEN’s low values are in part due
to his not entirely satisfactory method of investigation. I! is of
course also possible that the somewhat different conditions in re-
gard to transpiration and supply of CO, which the experiments
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