HARSHBERGER— STUDY OF THE CLOVERS. 147 



Plant I, Trifolium resupinatum (June i to June 4, 1908). — The 

 terminal leaflet was attached to the string at 8 A.M., June i. The 

 curve was fairly level until the middle of the afternoon, when it began 

 to rise with the approach of darkness. The steepest part of the 

 curve was reached during the night, gradually sloping downward 

 until morning. Some irregularities in the curve are noticeable on 

 June 2. These may be due to cloudiness, for other records show that 

 an overcast, or heavily clouded sky, causes the rise of the curve. 

 This is especially noticeable on June 3, for there is a sharp rise after 

 the depression of the morning. The sharp bumps in the curve of 

 Trifolium resupinatum indicate the nyctitropic movements of the 

 leaflets. The curve of Plant 2, T. subterrancum, demonstrates the 

 same response of the terminal leaflets. There was a steady rise on 

 June 3 in the afternoon, followed by a steep depression until night- 

 fall, when the up curvature during night becomes a marked elevation, 

 followed by a gradual depression until 9 A.M. on the following day, 

 June 4. 



Plant g. Trifolium leucanthum (Plate V). — Experiments with 

 this plant were started at 8 A.M. on June 2. The curve shows an 

 upsweep in the forenoon, followed by a downward curvature in the 

 middle of the day. At 3.20 P.M. we note a steep elevation, then a 

 drop with a steep rise to 6.15 P.M., succeeded by a sharp drop of the 

 curve and its reelevation during the night. The curve taken on 

 June 3 shows minor oscillations of the lever during the day and a 

 sharp rise at 6 P.M. for the night. With the approach of day the 

 curve drops uniformly until 8 P.M., when it rises slightly, dropping 

 again at 9 A.M. 



Plant 14, Trifolium alpestre. — This plant gave a curve which 

 started at 11.20 A.M., June 4. It shows a uniform rise to the middle 

 of the afternoon, then a drop and a sharp rise at nightfall. On the 

 morning of June 5 there is a uniform drop of the curve with some 

 oscillations until 3 P.M., when it begins to rise. 



Plant I/, Trifolium elegans (Plate V). — The curve of leaf move- 

 ments in this clover shows a gradual rise from the noon hour to late 

 afternoon, with a sharp upward curvature at night, followed by a 



PROC. AMER. PHIL. SOC, VOL. XLI. K. AUG, 3I, I922. 



