( 657 ) 
if it were at all possible diffuse into the surrounding space, which 
remained permanently free from carbon dioxide. This, however, did 
evidently not take place so fast, but that in all experiments starch 
was formed near the mercury. 
Nevertheless the possibility was not excluded, that a wider strip 
of starch might appear, if the carbon dioxide absorbing potash were 
absent. 
Such experiments were accordingly undertaken, and in order to 
make it possible that there should even be some accumulation of 
transported carbon dioxide, the inner bell-jar of the apparatus, which 
hitherto had been of a capacity of 3.2 litres, was replaced by one 
of only 0.8 litres’ capacity. 
In both experiments two halves of the same leaf were taken in 
each case. The two bases were placed in 3°/, carbon dioxide, one 
being exposed to the light and the other darkened. The two halves 
gave exactly the same result and the starch strips were not wider 
than in all the previous experiments, as is shown by the following 
summary : 
d 
TABLE: VI. 
Piant Number Duration | Width of starch strip in 
; of exp. of exp. both halves of leaves. 
| 
Dahlia (Cactus) Thuringia | XXXI 4 hours | 3—4 mm. 
Heliopsis laevis SEKI 4a. ol | 05-1 , 
It is obvious from all these experiments that with a number of 
leaves from widely different Monocotyledons and Dicotyledons a 
totally different result is obtained from that of the experiments 
described first. Carbon dioxide, even when abundantly supplied to 
the leaf base of these plants, cannot bring about the formation, at 
about 3 cm. distance in the apex of the leaf, of a wider strip of 
starch, than would have been formed without the addition of this 
carbon dioxide. Attention may further be drawn to a difference, 
which again clearly showed itself in these experiments, between the 
reticulate Dicotyledons and the parallel-veined Monocotyledons as 
regards the edge of the starch strips on the side nearest the apex. 
In all leaves with reticulate venation these edges were zig-zag and 
in most places sharply defined, owing to the presence of small veins. 
In the leaves of Grasses, of Acorus and of 7radescantia on the other 
hand there was a gradual transition to the starch-free apical portion, 
without any relation to veins, and there was no zig-zag border. 
