Day: position of dorsiventral leaves. 749 



Arisaema. 



Experiment 19. — A plant of Arisaema triphyllum, recently- 

 emerged from the bud, was placed in an upright position in the 

 dark chamber. At the end of 48 hours the leaflets had as- 

 sumed an epinastic position, with the tips pointing downward. 



Experiment 20. — A specimen of Arisaema was placed in a dark 

 chamber in an inverted position with the laminae horizontal 

 and the stem bound to a stick to prevent curvatures in that or- 

 gan. Forty eight hours later the tips had moved upward 

 through an arc of 30° -50 . 



Experiment 21 — A vigorously growing specimen of Arisaema 

 was attached to a clinostat and rotated with the stem in a hori- 

 zontal plane, and given an illumination from one side only. 

 Ninety hours later all of the leaves had curved through an arc 

 of 90 °, and were parallel to the stem with the tips pointing to- 

 ward the roots. 



Experiment 22. — A young specimen of Arisaema was placed 

 in an inverted position in a dark chamber and illuminated from 

 below in such manner that the light struck the dorsal surfaces 

 of the leaflets. At the end of a week no change in position 

 had taken place. 



Experiment 23. — Two specimens of Arisaema, as nearly alike 

 as possible, were placed in the dark chamber, one in the normal 

 upright position and the other inverted. No change in posi- 

 tion except that due to epinasty was noticed in the leaves of 

 either plant inside of a period of three days, and the angle of 

 curvature was the same in both. 



Experiment 21*. — A specimen of Arisaema was placed in such 

 a position in a dark chamber that the axis was horizontal and 

 the leaf blades in a vertical plane. The tip of one leaflet 

 pointed directly downward, while two others were directly up- 

 ward, but with the long axis of the leaf directed 20° away from 

 the vertical. Forty-eight hours later the leaflet pointing down- 

 ward had risen through an arc of 75° and lay nearly horizontal, 

 while the two remaining leaflets had curved downward to the 

 horizontal position. These positions were retained four days 

 later. 



Experiment 25. — Etiolated specimens of Arisaema exhibited 

 a great variety of positions of the leaflets, which seemed to be 

 dependent entirely on the trophies. In such condition the 



