NOTES. 
RESPIRATION AND ASSIMILATION IN CELLS CON- 
TAINTING CHLOROPHYLL. — It is a matter of common knowledge 
that free oxygen is essential to the continuance of active movement 
on the part of the protoplasm of the higher plants. An apparent — 
but only apparent — contradiction to this generalization is, however, 
furnished by the behaviour of the rotating protoplasm of an Elodea 
leaf when surrounded by an atmosphere of hydrogen gas. The 
experiment about to be described is a well-known one, but the con- 
clusions which can be drawn from it would appear not to be so 
generally appreciated as they seem to deserve. 
If a healthy leaf of Elodea be placed in one of those extremely 
convenient tubes designed by Professor Marshall Ward 1 , the move- 
ment of the protoplasm can be studied under favourable circumstances. 
Indeed it is possible to keep the same leaf, with its moving proto- 
plasm, under observation for several days. If a current of hydrogen 
be passed through such an apparatus containing a vigorous Elodea 
leaf, and the precaution be taken to dip the end of the tube through 
which the gas is escaping under mercury or water (to prevent the 
possibility of diffusion of air), it is clear that in a short time the 
pressure of oxygen within the chamber must speedily be reduced to 
what is practically zero. But if the experiment be conducted in the 
day-time, it is found that no arrest of the protoplasmic movement takes 
place. Indeed, in an experiment (which has been several times 
repeated in my laboratory), exposure to hydrogen from io a.m. to 
5 p.m. produced no effect whatever on the rapidity of the rotation 
within the plant-cells. 
1 See Phil. Trans. Vol. clxxxiii (1892), B, pp. 131, 132, where a description and 
figures of the apparatus here referred to are given. 
[Annals of Botany, Vol. X. No. XXXVIII, June, 1896.] 
U 
