HARSHBERGER— STUDY OF THE CLOVERS. 145 



them alone will reveal. The terminal leaflets of Trifolium lupinaster 

 and rcdinatum bend backward out of the vertical instead of forward. 

 The accompanying 62 drawings will demonstrate better than words 

 the actual position of the leaflets in the various clovers during 

 nyctitropism (Plates IV, V). 



Experimental Curves of Nyctitropic Clover Leaves. 



The elaborate and rather costly piece of apparatus used by Pfefifer 

 in his work, described and figured in Chapter II. of his work, was 

 replaced by a simple home-made piece of apparatus (kymograph) 

 consisting of a tin tomato-can mounted on an alarm clock with works 

 altered to suit the conditions of the experiments. The tomato-can 

 cylinder with registering paper was made to revolve once in two days 

 instead of once every twelve hours by changing the motion of the 

 bar turning the hour hand of the clock. The recording lever was 

 poised on a fulcrum fastened to a cork pushed into the mouth of a 

 test tube, which was then attached to the arm of a tripod, on the pan 

 of which the potted clover plant was placed. A fine thread was 

 attached to the clover leaflets by a thick solution of shellac and to the 

 short arm of the registering lever. The long arm of this lever being 

 twice as long as the short arm, the movements were thus magnified 

 twice. The downward movements of the leaflets were transmitted 

 into upward movements of the far end of the lever which traced the 

 curve of movement on the glazed paper, which was covered with a 

 coating of carbon by holding over a yellow gas flame after being 

 placed on the cylinder. The curves represented in the accompanying 

 figures were obtained in this way and were made permanent records 

 by passing the blackened paper through a solution of shellac in 95 

 per cent, alcohol. 



Fifty-five records were taken during the course of the experi- 

 ments with the kymograph. The species of Trifolium. the move- 

 ments of the leaflets of which were traced by curves, were as follows : 

 I, resupinatiim; 2, subterraneum; 3, incarnatmn; 4, pannonicum; 5, 

 elcgans; 6, reclinatum; 7, alpestre ; 8, spumosum; 9, leucanthuni; 10, 

 tridentatum ; 11, pannonicum; 12, lupinaster; 13, prafense; 14, al- 

 pestre; 15, hybridum; 16, medium; 17, elegans; 18, balansa: ; 19, 



