( 651 ) 
dioxide. He did not, however, examine the strip, 3 millimeters broad, 
which was in the grease between the edges of the crystallizing dishes. 
Now when Mr. ZijrsrrA examined the entire leaves, it became 
apparent that starch-formation extended continuously from the leaf 
base upwards over part of this strip, in an area bounded by a 
sharply defined line, somewhat like a zig-zag, but that it nowhere 
extended so far, that starch had also been formed in the space, free 
from carbon dioxide. The speakers observations were therefore 
confirmed, but were found to have been incomplete. 
When, however, Mr. Zamsrra repeated the experiment with a 
Dahlia leaf (exp. LV) the result was different. In this case also the 
starch-formation was found to extend into the greased strip, but in 
addition it extended here and there for some millimeters into the space 
freed from carbon dioxide. The border line of the starch reaction 
was here also somewhat zig-zag, but not everywhere equally sharp. 
Finally, when the experiment was performed with a leaf of 
Pontederia cordata (exp. LVI) starch-formation extended uniformly 
for 0.5 centimeters into the carbon dioxide free space. The limit of 
the starch reaction was in this case not zig-zag, but bent regularly 
and was not sharp, since the dark colour of the reaction disappeared 
towards the leaf apex by a gradual transition. Sranr’s cobalt test 
showed, that the stomata of the apex were closed at the end of the 
experiment. 
The possibility now existed that 
in these experiments the greased 
join had not been absolutely tight, 
although it was not very probable 
that this fault should have revealed 
itself in the experiments with 
Dahlia and Pontederia and not 
in others. In order to exclude 
this possibility two pieces of appa- 
ratus were constructed, which, 
with the aid of mercury, per- 
mitted of a completely airtight 
separation being effected between 
the space free from, and that rich 
in carbon dioxide. Both pieces of 
Figure 1. apparatus were used in the inves- 
tigation, but here the speaker will only describe the better of the 
two. (See fig. 1). 
In a Petri dish a, of 15.5 cm. diameter a smaller one 5 of 
