238 MR. 8. LE M. MOORE’S STUDIES 
upon the surface-wall has ceased in the latter, in the former 
rotation will be well established. Moreover, had the leaf been 
set in light just sufficiently strong to apostrophize the chloro- 
phyll of the remote cells without inducing rotation in them, those 
near the discoloured spot would have had their protoplasm in 
rotation; and if the quality of the light had been somewhat 
poorer, so that the epistrophe of the remote cells was not inter- 
fered with, the cells near the spot would have been the theatre of 
apostrophe. This latter fact was referred to on p. 218, and illus- 
trated in diagram 3 ; and if the explanation there given be sound, 
namely, that the proximity of a dead cell tends to diminish the 
vitality of protoplasm and consequently to increase its sensitive- 
ness to light, it will.not be less sound when extended to the other 
facts, which are of a closely allied nature. Thus we have a 
striking confirmation of the idea that rotation is but photolysis 
in a more violent form; and, moreover, the previously urged 
modification of Frank's notion that (abnormal) apostrophe is 
“a symptom of diminished vital energy” is seen to apply to 
abnormal rotation also. 
Rotation is well known as more readily setting in at the edge 
of Elodea-leaves than in the lamina*. This I am inclined to 
attribute to the early decay of the cells which project from the 
lamina to form the teeth, by which means the edge becomes a 
zone bordering on dead or dying cells—that is, a zone of abnormal 
rotation. 
On p. 226 it is stated that poisons cause apostrophe to set in 
more readily than under normal circumstances; they play the 
same part in respect of rotation. Thus if healthy Elodea-plants 
with epistrophized grains be placed in a solution of ferrous 
sulphate not strong enough to induce plasmolysis, many of the 
cells of still-attached leaves will have their protoplasm with all 
their chlorophyll grains in rotation within twenty-four hours, and 
within forty-eight hours rapid rotation will be general. This is 
true not only under positive conditions, but under negative also, 
removal to complete darkness immediately on placing specimens 
in ferrous sulphate sufficing to bring about rotation. Whether 
this is more quickly effected in darkness than in light has not yet 
been determined; though the few experiments which I have been 
able to make tend, upon the whole, to show that such is the 
* Usually the protoplasm of the midrib-cells enters earliest into rotation, 
Let i 
Es 
Se 
