HARSHBERGER— STUDY OF THE CLOVERS. 149 



ture to 6 P.M., when an upward movement is seen. The curve of 

 the lateral leaflet of No. 45 is generally up during day and down 

 during the night, with a steep downward gradient as the hour of 

 sunrise is approached, with a sharp upward curvature in the daylight 

 hours of the morning to 9 A.M. on June 11, then with a rainy morn- 

 ing, a downward movement is seen with an upward turn in the early 

 afternoon. 



Plant 48, Trifolium pannonicum (Plate \^). — The middle leaflet 

 of the compound leaf of this plant was connected with the kymograph 

 at II A.M., June 12, with an oscillating movement of the curve down- 

 ward to nearly 6 P.M., when the upward curvature during the night 

 is clearly traceable. Daylight of June 13 shows a valley-like depres- 

 sion with sharp irregularities and a strong upward turn at nightfall. 

 The same valley-like trough of the curve appeared for the daylight 

 period of June 14, with a sharp rise on the afternoon of that day. 

 Such sharp oscillations are inexplicable unless they are due to vari- 

 ations of temperature or humidity of the air. An inspection of the 

 several curves in the accompanying plate will give a more adequate 

 idea of the movements of the long arm of the recording lever. The 

 above description will serve to draw attention to the more important 

 features of the curves. 



The writer desires to acknowledge the help given by Professor 

 E. B. Ulrich in the arrangement of the details of the kymograph used 

 in the experimental work. The kymographs used in the study of the 

 clovers are essentially like the ones used by Professor Ulrich in his 

 study of the " Leaf Movements in the Family Oxalidacese," published 

 as a thesis^ in part fulfillment of the requirements for the degree of 

 Doctor of Philosophy at the University of Pennsylvania, received 

 June, 1910. 



EXPLANATION OF FIGURES OF THE SIX PLATES. 



(Plates I-VI.) 



1. resupinatum. 5. elegans. 



2. subterrancum. 6. reclinatiim. 



3. incarnatum. 7. alpestre. 



4. pannonicum. 8. spiimosum. 



2 Contributions from the Botanical Laboratory, University of Pennsylvania, 

 III. : 211-242. 



