( 656 ) 
The negative result thus obtained, could now, after the experience 
with the influence of darkening on the leaf base of Michhornia in 
experiment LII, be attributed to the fact, that the carbon dioxide 
absorbed by the base, had been wholly used up for starch-formation 
on the spot. Experiments were therefore also made, in which the 
leaf ‘bases were darkened with black paper right up to the edge of 
the fmereury, and therefore remained free from starch. But these 
experiments also gave exactly the same result; the strips of starch 
were equally wide in the leaves with bases in air containing much 
carbon dioxide, as in those with their bases in ordinary air. 
A survey of these experiments is given in the subjoined table: 
FABLE IV. 
Plant. | Number Duration | Width of starch strip 
of exp. of exp. | in both leaves. 
| | 
Triticum vulgare | XXIV | 6 hours | 1.5 mm. 
Zea Mays _ XXV ae Ae ae 
Dahlia Yuarezit | XXVI 5 » 4 n 
Aesculus Pavia | XXVII | Je, Sad ee 
Tradescantia virginiana XXVIII aya 1 h 
In order to eliminate more thoroughly possible inequalities between 
the leaves compared than could be done by careful choice, a few 
experiments were also performed, in which the longitudinal halves 
of the same leaf were used for comparison, and were darkened at 
the base. These experiments ‘yielded the same result, as given below : 
TABLE V. 
nee Ti EP ae ge - 
Plant , Number | Duration Width of starch strip in 
a | of exp. } of exp. both halves of leaves. 
eS 
Dahlia (Cactus) Thuringia XXIX 5 hours not noted 
Heliopsis laevis XXX | Den | 155. Mit. 
Finally two experiments may be mentioned, which were performed 
under conditions, similar to those of the last named, but in which 
the caustic potash was omitted in the smaller bell-jar. In all the 
previous experiments the carbon dioxide of the leaf apex would, 
