PROCEEDINGS 



OF THE 



Cmnkibgc |){plas0p{wHl Stadelg, 



Experiments on the Periodic Movement of Plants. By Miss 

 D. F. M. Pertz and Mr Francis Darwin. 



[Read 22 January 1900.] 



The first part of the paper is practically a continuation of the 

 authors' research " On the artificial production of rhythm in 

 plants" published in the Annals of Botany, 1891. The second 

 part deals with a new example of periodic movement. If a 

 "sleeping" plant is placed in a dark room after its leaves have 

 assumed the nocturnal position, it will "awake" next morning, 

 i.e. its leaves will return to the diurnal position, in spite of the 

 darkness. In the experiment described, the procedure was varied 

 by exposing the plants to one-sided illumination : under these 

 circumstances the leaves are well known to assume certain 

 characteristic oblique positions. The point of the experiment is 

 that if a plant is darkened after having responded in the above 

 manner to one-sided illumination, it returns to the oblique position 

 on " awaking" next day in complete darkness. 



Wealden Plants from Bernissart. By Mr A. C. Seward. 



[Bead 22 January 1900.] 



A brief account was given of a collection of plants in the 

 Natural History Museum of Brussels which were obtained from 

 argillaceous rocks at Bernissart, a locality rendered famous by the 

 discovery in 1877 of more than twenty complete skeletons of 

 Iguanodon. The beds containing the Iguanodons and plants 

 VOL. X. PT. V. 19 



