( 658 j 
It would certainly be going too far to deduce directly from these 
experiments, that the carbon dioxide, which is supplied to the base 
of these leaves, cannot at all contribute to starch-formation in the 
apex. Nevertheless the results obtained gave a clear indication as to 
further experiment, intended to show, beyond dispute, if possible, 
what was the state of affairs in these leaves. 
The way in which such experiments should be performed was 
now clear. 
The base of the leaf must be deprived of any supply of carbon 
dioxide, and the question was whether, as might almost have been 
expected from the above, a strip of starch would be formed above 
the mercury. If this were to take place, and in the same way as 
before, the proof would have been given, that the part of the leaf, 
placed under the mercury, itself produced the carbon dioxide, required 
for starch-formation in the adjoining part, which was exposed to light. 
The experiments which supplied an answer to this question were 
made by Mr. Zijrsrra in various ways. 
In the first place an experiment was made with the apparatus 
described above, but without the large bell-jar. A small leaf ot 
Dahlia Yuarezii (exp. XXXIIT) was placed in the apparatus in the 
ordinary way, but the base and the petiole were immersed in water 
which had been poured on the mercury outside the small jar. In 
the space free from carbon dioxide the apex now produced a strip 
of starch, similar in all respects to that in the experiments previously 
described, and in addition, a starch strip was formed under water 
in that part of the base which adjoined the mercury. 
Similar experiments were also made with a simpler apparatus, 
which moreover permitted of the water, in which the leaf base was 
placed, being kept quite free from carbon dioxide. 
Fig 2 gives a representation of this little 
apparatus. It consisted of a rectangular 
glass box, measuring 9 by 4.5 cm., and 
5 em. high, which is represented in the 
figure in section, the wall being indicated 
by 7. With resin and wax a vertical plate 
of glass was fixed longitudinally but it did 
not reach to the bottom. The box was 
filled with mercury to slightly above the 
lower edge of the glass plate G. The leaf 
Figure 2. B was introduced underneath the vertical 
plate, so that its base was on the right side of the figure. There a 
layer of boiled water W was poured on the mercury, so that the 
