1881.] natural sciences of philadelphia. 89 



April 26. 

 The President, Dr. Ruschenberger, in tlie chair. 

 Twenty-six persons present. 



A paper entitled " List of Fishes collected by Mr. W. J. 

 Fisher, npon the coasts of Lower California, 1816-77, with 

 descriptions of new species," hy W. X. Lockington, was presented 

 for publication. 



The death of Dr. J. Dickinson Logan, a member, was announced. 



Motility in Plants. — Mr. Thomas Meehan remarked that com- 

 paratively little knowledge of motion had been gained since the 

 time of Linnteus. The recent work of Mr. Darwin on the motions 

 of plants, was a A'aluable contribution to the subject, though con- 

 fined to motion in roots and leaves. He thought it would serve 

 the cause of science to note that the presence or absence of light 

 in itself could not, as so often assumed, account for all the phe- 

 nomena of motion. He had made numerous and careful observa- 

 tions, this season, on motility in Draha verna^ which plant, so far 

 as he knew, had not been observed to have an}' peculiarities. The 

 petals are usually closed during the early season, though the pedi- 

 cels are erect in the daytime, di'ooping so as to form almost a 

 perfect circle at night. These pedicels become erect about three 

 hours after sunrise when there is about twelve hours of sun in the 

 day, commencing to droop at about two o'clock in the afternoon.' 

 This diurnal motion in the pedicels continues some da^'s after the 

 petals have fallen, and apparentl}^ as long as the silicic continues 

 to grow. Later in the season, on clear days, the petals com- 

 mence to open early in the morning, contemporaneoush' with the 

 rising of the pedicel ; by the time this was erect, the petals Avould 

 be nearlj' expanded. The expansion, when the sun rose at half- 

 past five or six, would be complete by nine A. M. Strange to say, 

 no matter how clearlj^ the sun might continue to shine, the petals 

 commence to close about noon, and b}' about two P. M,, are com- 

 pleteh' closed. 



During the course of his observations, there was a period of 

 four da3's cloudy, and no attempt at expansion was made. The 

 fourth day, however, was so slightly cloud^^, that the eye could 

 scarcely look at the sun through the thin cloudj^ veil, The amount 

 of absolute light could be little less than on some days earlier in 

 the season, when the sun was wholly unclouded, but still there 

 was no attempt at expansion of the petals. Continued observa- 

 tions seemed to show that not mere light, but clear sunlight, was 

 necessarj' to the opening of the flower. 



One evening there was a heavy thunder shower ; the next da}- 

 7 



i 



