( 661 ) 
in their colourless parts a well-developed parenchyma, capable of 
producing by respiration a proper amount of carbon dioxide. If such 
leaves, after having been freed from starch, are smeared with cocoa- 
wax to prevent the escape of the carbon dioxide formed by respiration 
and are exposed to the light, borders of starch are developed in the 
green portions, at the edge of the colourless patches, in the same 
way as in the earlier experiments, but without any portion of the 
leaf having been darkened. Such experiments were performed with 
leaves of Cornus tartarica and Elaeagnus Frederici (exp. XLVI) 
and the best result was obtained with Pelargonium zonale (Mad. 
Salleroi) (exp. XLVII). 
It appears from the above, that in all the leaves investigated a 
transport of carbon dioxide was possible to a greater or lesser extent, 
and that this might lead to starch-formation in the portions of the 
leaf exposed to the light. The experiments were arranged in such a 
manner, that this starch-formation generally showed itself in more 
or less broad strips of the leaf. But the carbon dioxide which led 
to the formation of these starch strips was found to be of dual origin. 
In the majority of the leaves investigated, and in all the experiments 
of the various tables, except those of table 2, we had to assume, 
that the starch strips were exclusively formed at the expense of the 
respiratory carbon dioxide, which had been formed in the neighbouring 
darkened portions, hermetically shut off by mercury or by cocoa-wax. 
In the experiments with water plants, mentioned in table 2, the 
respiratory carbon dioxide must no doubt have also contributed to 
the formation of starch borders. These experiments did show, however, 
that another source of carbon dioxide also cooperated, namely the 
supply of carbon dioxide, which had been added to the air surrounding 
the leaf-base, which was absorbed by this base, and which was trans- 
ported through the 3 cm. long portion of the leaf under the mercury 
into the space free from carbon dioxide, and was assimilated there. 
In other words: in most leaves, of J/onocotyledons as well as of 
Dicotyledons, only a very limited transportation of carbon dioxide 
is possible. But in these leaves one has an excellent method for the 
study of this transportation, by utilizing the respiratory carbon dioxide 
of the adjoining parts. 
In a few parallel-veined leaves of water plants on the other hand, 
a much wider transportation is possible, which can be demonstrated 
with the relatively rough apparatus employed. 
The question now arose, how these two varieties of carbon dioxide 
transportation must be imagined and on what the difference of the 
two categories of leaves referred to, depended, 
