(655 ) 
In the above experiments the leaf base in the space with much 
carbon dioxide was exposed to the light and accordingly this part 
of the leaf was full of starch at the end of the experiment. We 
might now expect that on darkening the leaf-base, more carbon 
dioxide would remain available for transport to the apex, and that 
a wider strip of starch would be formed than in the former case. 
If this expectation were realized, it would be an additional proof, 
that carbon dioxide is transported from the base to the apex. An 
experiment, carried out with the two longitudinal halves of the same 
leaf of Lichhornia (exp. LIL) indeed gave proof of this. Here both 
bases were kept in air with 2°/, carbon dioxide, but one was 
darkened, the other not. In the latter case less carbon dioxide 
remained available for transport on account of the consumption 
of carbon dioxide for starch-formation in the base, and in the course 
of 4 hours a strip of starch , 2—5 mm. wide, was formed in the 
upper part of the control half, as compared with one 5—8 mm. 
wide in the other half of the leaf, of which the base had been 
darkened. 
In these experiments the strip of starch never had anything like 
a sharp edge on its upper side, nor was there any connexion between 
the limit of the reaction and the veins. The reaction simply became 
weaker and weaker at the edge of the strip and soon stopped completely. 
A series of experiments with other leaves yielded, however, a 
totally different result. Here the strip of starch in the two leaves 
experimented on was always equally wide, no matter whether the 
leaf base had been placed in ordinary air or in air with a high 
carbon dioxide content. 
In some of these experiments leaves of the same plant individual 
were taken, in each case as nearly as possible equal. The subjoined 
table summarizes them. 
TABLE III. 
—- — << qh: fe TT —— — = —— 
Plant | Number ‚ Duration, | Width of the starch 
à of exp. | of exp. strip in both leaves. 
Sambucus nigra | XIX | 5 hours 3 mm, 
Juglans regia XX | er An | l £ 
| 
Acorus Calamus XXI | ale 2 se 
Zea Mays XXII | Oi | VD orn 
Hordeum vulgare XXIII Ps | | ™ 
