MR. A. J. EWART ON ASSIMILATORY INHIBITION, 405 
poisonous action of an atmosphere of CO,. Specimens of the 
above three mosses were kept in moist atmospheres of hydrogen 
and CO, at a temperature of from 15° C. to 20° C. in the darkness 
for long periods of time, and then examined. 
The mosses are kept moist in a suspended tray within a gradu- 
ated bottle which is filled with water. Gas is driven in, driving 
out water through the exit-tube the shorter distal end of which 
dips under mercury and leaving the receiver filled with the gas 
in question. In the same way, à mixture of gas with air or 
oxgygen in any given proportion can be readily introduced and 
when necessary, by first siphoning or driving water backwards 
and then driving it out again, fresh gas can be introduced with- 
out an exposure of the plants to the air being necessitated. 
TaBLe R. 
| 
| l week in darkness in 4 weeks in darkness in 
| atmosphere of H. 75 p.c. CO, + 25 p.c. air. 
Bryum | Nearly all leaves and leaf- | Most leaves and leaf-cells | 
cespititium. cells living and normal.” living. In a few leaves | 
Assimilation in a few| assim. is very weak, but 
leaves weak, but in rest} in rest is active. 
active. 
Orthotrichum | Many older leaves and leaf-| As in Bryum. 
affine. cells dead. Living leaves 
assim. absent or in parts 
only. Apical young leaves | 
assim. is mod. active. In | 
1 day in D. Ch. in air, | 
assim. aetive in most cases | 
and in 2 days in all. | 
| Dicranum Only apical leaves living,| Most leaves and leaf-cells | 
scoparium. wholly or partly. No) living. Weak assim. in| 
assim. In 1 day weak| young leaves, in older) 
assim. in few leaves, in| leaves none. In 1 day) 
2 days weak in all leaves,| assim. in all living cells, | 
| active in some, and in which in 2-3daysisnormal | 
4 days active assim. in all} and starved appearance of | 
| living leaves. cells disappears. | 
l 
For comparative purposes, plants were also kept for 4 weeks 
in darkness in moist air at 15°C. On examination, the leaves of 
these were found to be almost all living and showed fairly active 
or in a few cases only weak assimilation. The chlorophyll grains 
are, beyond having a slight yellowish tinge and being devoid of 
starch, normal, whilst the protoplasm is clear, vacuolated, and 
