108 



BIOLOGY OF PLANTS. 



That the electrical powers thus developed must exert a 

 constant and powerful agency upon the growth of plants, ap- 

 pears from the fact, that electricity is a most efficient pro- 

 moter of endosmosc or absorption. Endosmose is a term, 

 which Mons. Dutrochet has given to a peculiar power which 

 he discovered in experimenting upon the permeability of tis- 

 sues. Its name is from the Greek, and signifies intei-nal im- 

 pulse. It seems to be a property possessed by all thin, mem- 

 branous substances, when liquids of different densities, and 

 electro-motive powers are placed on each side of the mem- 

 brane. The following is a mechanical illustration of this cu- 

 rious property. 



Fig. 13 represents 

 the endosmometer. It 

 consists of a small bell- 

 glass receiver a, with 

 a glass tube c, open at 

 both ends, and accu- 

 rately fitted to the ap- 

 erture in the top c. 

 Over the mouth of the 

 receiver is stretched 

 any membrane, as a 

 fresh bladder ; and a 

 metallic substance, e- 

 ven and firm, with aper- 

 tures punched through 

 it, is placed upon the 

 membrane as a support. The receiver may then be filled 

 with sweetened water, molasses, or almost any substance 

 denser than water, through the cork c. The receiver must 

 now be placed in a vessel of water 6, so that the water on the 

 outside of the receiver shall be at the same height with the 

 substance within. If now this is suffered to remain, the mem- 

 brane will draw in the water, and force it up the tube, as 



