244 MR. 8. LE M. MOORE'8 STUDIES 
afternoon of the third day all movement had ceased. Light was 
then admitted until the protoplasm recommenced to rotate, 
when the agency of darkness was again invoked, after which 
stasis again set in. The process is, in fact, capable of apparently 
indefinite repetition. 
Preliminary Study of the Influence of Light upon Rotation. 
The many points of agreement between photolysis and rota- 
tion render very noteworthy the dictum of Hofmeister*, that 
increase in the intensity of light does not markedly accelerate 
protoplasmic movement. The interest accompanying this state- 
ment, which is not pronounced affirmatively against by either 
Sachst or Pfeffert, is discovered when account is taken of its 
direct contradiction to another statement, easily verifiable, with 
respect to photolysis, viz. that the further a plant is placed in the 
photrum to the right of its positive critical point, the more rapidly 
will its chlorophyll be apostrophized. Moreover, it has been 
seen that the higher the illumination to which an Elodea-leaf 
with epistrophized chlorophyll is exposed, the sooner will rotation 
ensue in its cells. If, therefore, the inception of rotation is 
governed by the intensity of light, its continuance ought to be 
affected by that agency. 
In experimenting on this subject there is one matter requiring 
careful attention. In order that the effect of enhanced illumina- 
tion may be brought into view, it is necessary that the rotating 
stream be moving at a rate much below the maximum ; if its 
speed be great, very little, if any, acceleration will ensue in higher 
light, because, just as a definite quantity of work and no more 
ean be got from a machine, so only a certain velocity can be im- 
pressed upon protoplasm. It is this capital point which has been 
overlooked by all experimenters. So far as the after-mentioned 
observations made with it in view go, a marked acceleration of 
rotation takes place in light of improved quality. The way in 
which this kind of experiment is usually conducted may be 
instanced as follows. Upon a September afternoon, the tempe- 
rature of the room in the shade being 70? F., rotation was well 
* * Pflanzenzelle,' p. 49. 
t * Vorlesungen,’ Chapter xxxv. 
] ‘ Pflanzenphysiologie,’ ii. p. 386. 
= 
