( 650 ) 
mesophyll led to the supposition, that the transport of the carbon 
dioxide so taken up, need not be impossible. 
A want of further experimental data made this question remain 
unsolved up to the present. The necessary data have now, however, 
been collected in the investigation of Mr. Zijrsrra, who has shown 
that the facts, previously observed by the speaker, had indeed been 
correctly described, but that other results may also be obtained, 
provided one works with different plants from those which the 
speaker happened to have used, or arranges the experiments in a 
different way. Mr. Zirsrra was able to show that in the experiment 
described, starch-formation may sometimes indeed occur in the space 
free from carbon dioxide. The above conclusion as to the impossibility 
of starch-formation at the expense of carbon dioxide derived from 
the immediate vicinity, has therefore been found to be incorrect. 
The other results formerly obtained by the speaker, and especially 
the chief deduction, regarding the impossibility of starch-formation in 
the leaves at the expense of carbon dioxide, taken up by the roots 
from a soil rich in humus, were, however, completely confirmed and 
further elucidated by. Mr. Zuusrra’s investigation. An explanation of 
the experiment described above, was also suggested and generally 
speaking Mr. Zuusrra succeeded in solving pretty completely the 
question of the possibility and occurrence of carbon dioxide transport 
in leaves. How this was done the speaker wishes to communicate 
below. 
Not unnaturally it seemed desirable to begin the investigation with 
a repetition of the above described experiments. 
This was first done with the leaves of Polygonum Bistorta and of 
Cucurbita Pepo (experiment LUI and LIV}'), which were also employed 
by the speaker in his above-mentioned investigation. In these and in 
all later experiments Mr. Zirsrra demonstrated the formation of 
starch by the so-called Sacus-ScuimmpER metbod, according to which 
the entire leaves, after decolorisation, are examined for starch content 
with the help of an iodine-chloralhydrate solution. This method was 
unknown in 1877, so that the speaker used microscopic sections, 
which is very cumbrous and gives less complete, albeit equally 
certain results. 
The speaker limited himself to applying the starch reaction to 
sections of the apex of the leaf, which was in the space free from 
carbon dioxide, and to the base, which was in the air rich in carbon 
1) The numbers of the experiments are here and in what follows the same as 
those in Mr. Ziustra's paper. 
~ ae 
