64 Dr. H. T. Brown and Mr. F. Escombe. [Jan. 9, 
In the following Table XIII are recorded the results of two assimilatory 
experiments on leaves which have their stomata on one side only. In 
Nuphar the stomates are on the upper, and in Catalpa on the lower side of 
the leaf. 
Table XIII. 










| 
Area in | CO, 
Time square | assimilated, 
Plant. ; ; : : 
in hours. centi- in cubic 
metres. centimetres. 
(1) Nuphar advena (hyperstomatous) ...... 2-0 76°97 U. 2:20 
L. 0:00 
(2) Catalpa bignonioides (hy postomatous) 1°85 79°03 U. 0:00 
| L. 4:91 
(3) x Bs Wee 79°03 U. 0:00 
L. 8°96 

The results fully confirm in most respects the observations of Blackman, and 
may be summarized as follows :— 
(1). In the respiration of amphistomatous leaves (e9., Canna indica and 
Rumex alpinum, see Table XI) the ratio of the carbon dioxide evolved from 
the upper and lower surface of the leaf follows very closely the ratio of the 
distribution of stomates. 
(2). In the assinulatory process of amphistomatous leaves illuminated on 
the upper surface (see Table XIII), the intake of carbon dioxide by the 
lower surface is always less than might be expected from the relative number 
of stomata on the two sides, the amount of carbon dioxide assimilated by the 
under side in some cases falling to half that deduced from a consideration of 
the stomatic distribution. 
(3). If the leaf is hypostomatous (vide Catalpa, Table XIID), the intake of 
carbon dioxide during assimilation only takes place on the lower (stomatifer- 
ous) surface. 
(4). When the leaf is hyperstomatous (vide Nuphar, Table XIII), the 
intake of carbon dioxide is only on the upper (stomatiferous) surface. 
That there should be a much closer correspondence between the ratios 
of stomatic distribution and the ratios of gaseous exchange in the respiratory 
than in the assimilatory process, follows from what we know of the physics of 
diffusion through fine apertures. 
Assuming that there is a steady evolution of carbon dioxide going on 
