Notes. 
1 66 
amounts of C 0 2 exhaled closely follow the ratios of the numbers of 
stomata. 
A few examples in illustration of this may be given. 
A. 
B. 
C. 
Ampelopsis hederacea 
O 105 
° °° ^ c.c. C 0 9 per hour and 10 sq. cm 
0.100 2 F 4 
3 
100 
Alisma plantago 
*35 
100 
0.030 
0.025 4 
120 
100 
Iris germanica ...... 
100 
0-029 
110 
100 
0-026 5 ” ” 4 
100 
Ricinus communis . . . 
100 
250 
0-015 
„ „ „ 10 sq. cm. ...... 
0-037 ' 
100 
260 
Column A gives the proportionate number of stomata on the two 
surfaces; B the amounts of C 0 2 exhaled by these; C the ratios of 
these amounts. Each experiment lasted about fifteen hours. 
Experiments on the absorption of C 0 2 during assimilation showed 
the same close relation to the distribution of stomata. For these 
experiments a constant fixed amount of C 0 2 must be introduced into 
the air stream supplied to the leaf, which makes the experiments 
much more complicated. 
As hitherto carried out, direct sunshine, continuous for several 
hours, has been essential for the success of these experiments. They 
are, consequently, but few in number, though perfectly clear in their 
interpretation. 
In an experiment on the leaf of Ampelopsis hederacea with no 
stomata on the upper surface, air containing i-6 per cent. C 0 2 was 
supplied to both surfaces at the rate of 22 c.c. for every fifteen 
minutes; of the 0-37 c.c. of C 0 2 entering the capsule on the lower 
surface 0*14 c.c. was absorbed in, while none at all was absorbed by 
the upper surface. With a leaf of Alisma, on the contrary, the 
whole of the C 0 2 — 0-15 c.c. — supplied in fifteen minutes to the upper 
surface was absorbed, and o-i 1 c.c. of that supplied to the lower. In 
this leaf the stomata are in the ratio of 135 above to 100 below, to 
which ratio the absorption numbers closely correspond. A very 
