( 654 ) 
2—3°/, of carbon dioxide, and the other in ordinary air, containing 
therefore very little carbon dioxide. 
If the hypothesis just brought forward were correct, one ‘might 
expect that owing to a more copious supply of carbon dioxide, a 
wider strip of starch would be formed in the former case than in 
the latter. It did not seem probable that the increased supply of 
carbon dioxide would manifest itself by a stronger iodine reaction, 
for, as we have seen, in most of the experiments described above, 
the reaction, if it appeared at all, was as strong as possible. 
These comparative experiments were carried out with two sets of 
apparatus of the kind deseribed, both of which were provided with 
a large bell-jar, including therefore the one in which the leaf-base 
was in ordinary air. This was done in order to maintain as far as 
possible the same temperature in the two smaller jars, for it was 
found that in these experiments the temperature had a great intluence 
on starch-formation. 
The result of these experiments varied considerably in different 
plants. In some cases it could be definitely shown, that carbon 
dioxide, supplied to the base, had influenced the manufacture of 
starch in the upper part of the leaf, but this could not be demon- 
strated for other plants. 
The speaker first considers the experiments with a positive result, 
summarized in the following table: 
TABLE II. 
== Nl — ——E nn ee — EE = = 
Width of the starch strip 
Number | Duration | in the CO, free space. 
Name. of ex- of ex- | 
periment. | periment. Base | Base in 
2 COR ordinary air. 
nn 
Pontederia montevidensis XLVIII | 7 hours, G/)) sam. 2 mm. 
Eichhornia speciosa XLIX 7 5 laet iem: Zen 
” ”» L 51/, ” | 1,5 ” 1 ” 
Eucomis punctata LI 9 " | 1 5 3% 
The first two experiments were carried out with leaves which 
were as nearly as possible equal, and the last two each with the 
halves of one and the same leaf. 
All these experiments very clearly demonstrate the influence of 
the increased supply of carbon dioxide by the formation of wider 
strips of starch. 
