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completely covered with cocoa-wax and then, here and there, with 
strips of paper of various widths; between these strips portions of 
the leaf remained exposed to the light. 
‘Borders of starch were then formed along both sides of the black 
strips of paper, since the respiratory carbon dioxide, formed under 
the paper, escaped on both sides. The width of these starch borders 
was slight in the case of the narrowest strips of paper, because 
beneath these but little carbon dioxide was formed; it increased 
with the width of the strips and of course reached its maximum as 
soon as the half-width of the black strip of paper corresponded 
more or less to the maximum distance through which carbon dioxide 
could pass during the time of the experiment. The half-width of 
that strip of paper, at which the starch borders just reached their 
maximum width, was therefore a measure of the distance through 
which the carbon dioxide in the leaf could pass under the given 
conditions. 
Such experiments were first made with parallel-veined leaves, in 
which the carbon dioxide transport was only limited by the small 
dimensions of the intercellular spaces. The result was, that in 7’riticum 
(exp. LVII) the carbon dioxide could be transported in 6 hours over 
at least 2.5 cm., in Acorus (exp. LVIII) in 6 hours over rather 
more than 1 em, in Tradescantia (exp. LIX) in 5 hours over less 
than 1.5 em. There is every reason for the assumption, that in 
these leaves, in experiments of longer duration, somewhat higher 
values might have been obtained. 
In net-veined Dicotyledonous leaves the case is somewhat different, 
for, as we have seen, in consequence of the absence of inter- 
cellular spaces from veins of a certain order, the carbon dioxide 
transportation is strictly limited to definite areas, the size of which 
may be very different in different leaves. If these areas are minute 
we observe with the narrowest strips of darkening paper also the 
maximum width of the starch borders, the absolute dimensions of 
which are likewise minute. 
This was the case in Juglans, Aesculus and Tilia, in which the 
distance of the transport could not be accurately determined, but 
certainly did not exceed 2—3 mm. 
In Dahlia and in Sambucus the transport areas referred to are 
relatively very large, the starch borders along the narrowest strips 
of paper are narrowest, and they increase to a certain maximum 
width -along the wider strips. Here, however, this method cannot 
give very accurate results. For if a transport area is darkened over 
its greater part, ther much carbon dioxide is indeed formed in it, 
