120 Ingvar Jorgensen and Walter Stiles. 
those where the stomata were limited to the lower surface only and 
those where the stomata were present on both surfaces. Usually 
the carbon dioxide evolved from the leaf into a current of air free 
from that gas was the quantity measured, but results were also 
obtained for the intake of carbon dioxide which show the path 
traversed by the gas is the same whether it is travelling into or out 
of the leaf. 
In the following table we have summarised the results obtained 
by Blackman for the ratios of the amounts of carbon dioxide given 
out from the two surfaces of the leaves of various plants. 
Table III. 
Peculiarity. 
Stomatic ratio. 
CO s respired. 
Plant. 
Upper surface 
Upper surface 
Lower surface 
Lower surface 
Nerium oleander 
Very thick cuticle 
0 
3 6 
too 
100 , 100 
Prunus laurocerasus 
J) I II 
0 
100 
0 4 
100,100 
Hedera helix 
>1 II II 
0 
Too 
4 
Too 
Platanus occidentalis 
Thin cuticle 
0 
Too 
3 
100 
Ampelopsis hederacea 
II II 
0 
100 
3 
100 
Polygonum sacchalinense 
II II 
0 
lob 
6 
Too 
Alisma Plantago 
Aquatic plant. 
More stomata on 
185 
100 
135 120 
100,100 
115 113 
upper surface 
100,100 
Iris germanica 
Isobilateral leaf 
100 
100 
105 110 
100 , 100 
Stomata on both 
100 
575 
100 
375 
Populus nigra 
surfaces, fewer 
on upper 
Helianthus tuberosus 
II 
100 
240 
100 
273 
Tropoeolum inajus 
II 
100 
200 
100 
265 
The numbers in the foregoing table show how constantly the 
path of carbon dioxide from the leaf follows the distribution of the 
stomata. Similar results were obtained in the case of carbon dioxide 
absorbed in assimilation. Thus, in the cases of Ampelopsis 
hederacea, Platanus occidentalis and Polygonum saccJialinense, 
where all the stomata occur on the under surfaces of the leaves all 
the carbon dioxide was found to enter by the lower surface. None 
