June, 1906.] Diurnal Rotation in Leaves of Marsilea. 555 



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 the}' 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. 



