( 221 ) 
with a coefficient of about 3. The observations at 0° are the least 
reliable, for here the quantity of CO, is smallest, so that the error 
of the apparatus, which amounts to about 0.7 mg., has the greatest 
influence. I have, however, not thought it advisable to make a 
correction for this error, as the individual differences of the plants 
used are much greater. 
It is evident from the figures 
that at 0°, 5° and 10° the respi¬ 
ration is constant in successive 
hours; between 15° and 20° some¬ 
thing of a rise may frequently be 
hour noted. (Fig. 1). 
Fig. L Respiration at 15° G. The curves at 2b° and especially 
at 30° show an irregular course ; the Ugures quoted in the table for 
25° decrease somewhat; others 
show the irregularity more. 
Fig. 2 represents this irregular 
variation at 30°. We may here 
, remark that at 30° growth is 
optimal and can for instance be 
t- 
—- 1 
Lx 
d 
Fig. 2. Respiration at 30 c 
readily detected with the naked eye after 6 hours. 
At 35° respiration falls off pretty rapidly during the first hour and 
afterwards continues to oscillate more or less; on the other hand the 
falling off persists at 40', 45° and 50°; the curves somewhat resemble 
logarithmic ones (fig. 3) although, as far as I have been able to 
ascertain, they do not satisfy such a condition mathematically. The 
absolute and the percentage decline becomes larger with rise of tem¬ 
perature. Between 35°—50° therefore a harmful factor makes its 
appearance, so that at 25° and 30° there is neither a rise nor a 
decline whereas a rise may be detected at 15°—20°. 
Notwithstanding Blackman’s theory, there is some point in 
investigating the optimum of respiration, because it has been a 
point of dispute between various observers. The principal records 
are those of Kreusler 1 ) and of Clausen’). 
Kreusler found no optimum for branches of Rubus; the res¬ 
piration rises to the temperature limit of life, and this is the view 
which has been accepted in most text books. The highest tempera¬ 
ture observed was 46°.6 C. 
Clausen found for Lupinusluteus an optimum at 40°. I wish to 
*) U. Kreusler, Landwirtsch. Jahrbucher, Bd. 16, p. 711, 1887. 
2 ) H. Clausen, Landwirtsch. Jahrbucher, Bd. 19, p. 893, 1890. 
