88 
higher degree rain impedes the reduction of carbonic acid — 
and accordingly lowers the figures, as shown in the table at 
p. 81. It would seem far more likely that the transmission 
of organic matter in the daytime, which was demonstrated — 
by Moll‘) and Sachs*), is many times greater than during 
the night. 
But this centripetal current is hardly observable during the 
day. That, however, this current must be of importance, is 
evident from an experiment by Sachs, who found that in 5 
hours at 23°—37° C. the whole rest, which six morning hours 
at a temperature of 15°—25° C. had produced, disappeared 
altogether. How much, then, must not disappear from the leayes- 
which are continually shone upon by the blazing tropical sun! 
In his repeatedly quoted ,Beitrag zur Kenntniss der Ernib- — 
rungsthétigkeit der Blatter” Sachs lays especial stress on the 
fact that the gain obtained in a given space of time, is merely 
the difference between what has been assimilated and what has 
been transmissed. Do the figures arrived at teach us anything 
beyond this difference? To be sure, by no means the numbers 
to be subtracted from each other. In the garden at Buitenz0lg 
the examined plants *) merely showed, that in the first morl- 
ing hour the transmission surpasses the assimilation and that 
later on the latter process predominates. After 12 o'clock the : 
plants behave differently according  s their leaves remain iD 
the direct sunlight or get into the shadow of others which up 
to that time were out of the sun. Shrubs , trees and many : 
climbing plants are in this case: about 12 o'clock they show 
the greatest difference in the direction of assimilation; this iy 
1) Landwirthschaftliche Jahrbiicher VI, p. 848: 
2) 1. ©. p. 15, : 
3) I beg leave once more to emphasize the fact that four of the plants ape 
beyond doubt, but that the observation was made too late to allow of 
tional experiments in this direction. 
