June, 1906.] Diurnal Rotation in Leaves of Marsilea. 
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were not merely inclined toward the west but were squarely 
facing in that direction. 
At five o’clock the next morning when the day was just 
dawning they were observed again. The leaves were still 
tightly folded in their night position. None of them were facing 
the west as they must have been the night before when they 
folded up. On the contrary a large proportion of them had 
turned and were facing the east. But in this respect there was 
no uniformity in position as there had been in facing west the 
night before. In the light of the following observation, I inter- 
pret this to mean that they were just in process of turning from 
the west to the east under the influence of the increasing illu- 
mination. 
At 7:30 on my return from the farm I found that all the 
leaves were spread out toward the east as they had been to the 
west the night before. Many thousands were seen and among 
them all there was not a single exception. The effect was very 
striking indeed. 
The only other opportunity that was offered for observation 
was a few minutes after two in the afternoon of a cloudy day 
about an hour after a thunder shower. At that time all of the 
leaves were spread out parallel to the ground. 
I have several times watched other species of Marsilea but 
have never succeeded in detecting similar movements. It 
would be most desirable to determine under what special condi- 
tions, if any, this phenomenon took place. Perhaps it is a 
peculiarity of the particular species or variety found at Victoria. 
An examination of the leaves to determine in what region 
the motion took place showed that it was not due to tortion or 
other movements of the petiole which remained erect and 
unchanged through the whole process. The motion is rather in 
the individual leaflets which are turned by the twisting and 
bending of their petiolules which also cause the folding up of the 
leaves at nightfall. We have then in these petiolules an exceed- 
ingly interesting motile area similar to that found in the Seed 
Plants, 
