sleep condition mi^'lit answ.-r. vonld it uniy Ix' itrovcn Unit no 

 stinnilns is responsible for it. or tluit no ;i(l\;int;i^(' is {^Mincd hy 

 assuming sueli a i)osition. 



It is geiu'i-aily Itclicvctl that sleep movements ai-e adjust- 

 ments to environment, either to diminish radiaticm or to facili- 

 tate shedding of water, such as dew. There is, therefore, no 

 reason for believing that a neutral position exists. On the con- 

 trary, the leaves are probably continually in adjustment to 

 external conditions or stinnili. 



Experiment showed tiiat tlie facts warranted the conjecture 

 that greater consumption of time was found to be necessary for 

 the leaflets of Ethyrina to return to the expanded condition. 

 The previously-mentioned plant of low stature was used for the 

 test, but so much variation existed among the different leaves 

 that very definite results were not possible. Some leaves re- 

 sponded fairly quickly, so that in twenty minutes they were 

 nearly expanded. At the end of this time, however, others were 

 half expanded, while yet others were turned upward, having 

 shown little or no inclination to change position. 



If leaves were artificially placed, in unusual relation to sun- 

 light, the tips of the leaflets continued to point toward the light. 

 A leaf with its back or spongy parenchyma up. turned its 

 leaflets vertically toward the sun, thus bringing the spongy 

 sides of the lateral leaflets together. If a leaf is turned edge- 

 wise to direct sunlight, with the midrib perpendicular to the 

 rays, a movement of the terminal leaflet occurs, although it is 

 already in a protective position. It deflects its tip ujiwards, its 

 surface being maintained in the same plane. A bend in its 

 pulvinus of less than ninety degrees is the rule. The lateral 

 leaflets remain stationary. Both are protected, and one has its 

 tip directly toward the light. The lower leaflet has its tip 

 pointed downwards. It would be a difificult matter for this 

 leaflet to turn its tip toward the light, for it would have to 

 swing into the horizontal position first, or else rotate its pulvinus 

 one. hundred and eighty degrees. The first alternative would 

 bring its surface perpendicular to the sun's rays, which, of 

 course, it is trying to avoid. The second is not within the power 

 of the pulvinus. Another factor, probably of greater importance, 

 and doubtless the real reason for the leaflet's stationary position. 



