32 Memorias de la Sociedad Científica. 



vitalistic theories. I find but one entirely general cause : the 

 delay of the protoplasmic currents in wicli life consists, as I 

 stated in a special paper on this subject.' v 



The Sleep of Plants. 



In animáis sleep is cliaractei'Ised by tlie flaccidity of tlieir 

 locomotor organs, wliilst leaves remain in tlieir nocturnal sta- 

 te on account o£ a very remarkable rigidity tliat seizes tliem. 

 Linnaeus once received from Prof. Sauvageau o£ Montpellier 

 a shoot o£ Lotus ornithqpodioides L., wliicli began to fiourisli 

 in a liot-liouse at the garden of Upsala. The great botanist 

 examined the flowers directly they oponpd and observed that 

 they disappeared on the same night. He believed at first 

 that they liad been thoughtlessly cut awíny, but had to ack- 

 nowledge his mistake next day, as the disappearance of the 

 flowers at night dependes completely on the cióse approach 

 of tlie adjoining leaves which form a kiud of shelter £or theni. 

 This observation aft'orded cause for fresh investigations, and 

 it was discoverell that every species of plants opens and shuts 

 itgelf at an appointed hour, etc. 



Explanaüon. — "The motoi- dilatation occurrlng in some 

 leaves at the base of the petiole is due to two antagonistic 

 factors, the one tending to raise the leaP, the other trying to 

 bend it, but the former, being by n ature the weakest, acqui- 

 res an additional forcé whenever liglit and heat, éndo\\'ed wilh 

 a certain degree of intensity, produce aii abundance of sap ia 

 the cells which incrcases the turgescence : it cau then resist 

 the action of the opposlte factor." In short, this is but a me- 

 chanical ■ efEect of the dolar of the nuti-itive currents coming 

 up the leaves. 



1. "Protoplasmic Cuvi-euts aud Vital Voia^," Xatural Science, AprillSOí). 



