240 MB. 8. LE M. MOORE’S STUDIES 
The Effect of Sectioning on Rotation. 
Frank* has ascribed rotation in its best exhibited form to the 
sectioning which is usually practised in order to see it. This idea 
is quite erroneous ; for not only can protoplasm be set in rota- 
tion without any injury to the plant, but under certain con- 
ditions sectioning can be practised without rotation following ; 
that is, the result can ensue without the intervention of the 
supposed cause, which latter does not necessarily carry rotation in 
its train. 
As an instance of the way in which wrong notions upon this 
subject can be generated, the following experiment may be cited. 
Longitudinal and transverse sections of neighbouring Elodea- 
leaves were divided into four sets; two were mounted in water 
on a glass slide and covered with cover-slips, two placed in shallow 
vessels filled with water. One from each of these two was imme- 
diately removed to darkness, the others being brought up to a 
window on a dull August day, temperature in both cases 66°5 F. 
Examined an hour later, the temperature at the window having 
meanwhile risen to 67°, it was found that rotation was fairly 
general over the illuminated portions of leaf, and was well estab- 
lished in the cells on the section-edges of the darkling ones. The 
inference from this was obvious: it was only when attention was 
paid to the fact that in the neighbourhood of discoloured cells of 
the darklings vigorous rotation had sct in, there being spaces of 
quiescent protoplasm separating the disturbed areas from each 
other and from the cut edge, that the existence of some cause for 
rotation other than mere sectioning was suspected ; otherwise, 
why should the areas of disturbance be scattered, seeing that on 
the section hypothesis rotation should appear first at the section- 
edge, and progress therefrom uniformly over the leaf ? 
In fact, it usually happens that .Elodea-leaves sectioned longi- 
tudinally, transversely, or obliquely, within an hour of the opera- 
* Pringsheim’s Jahrb. f. wiss. Bot. Bd. viii. So anxious was Frank to 
emphasize the effect which preparation has upon rotation, that although he 
observed rotating protoplasm in the internal cells of uninjured Vallisneria- 
leaves, he maintains that this form of rotation differs from that which ensues 
upon sectioning, inasmuch as only a few of the chlorophyll grains are carried 
into the stream. Had he allowed more time and used better light, he would 
have found this alleged difference to be purely imaginary. 
