PEOPAGATIOK OF PLANTS. 17. 



" While some of the little cells are at work on delicious 

 honey and rare perfumes, others are engaged in com- 

 pounding healing medicines and even deleterious poisons." 

 It is quite within the range of possibilities that plants 

 possess the power of discrimination or choice, irrespec- 

 tive of their mechanical structure, and this may, in part 

 at least, account for their responsive action to certain 

 stimulants and not to others. Of course we are not to 

 suppose that plants possess any functions corresponding 

 with mind in animals, but they do possess a sensitiveness, 

 which often nearly approaches, if it does not quite reach, 

 the realms of intelligence. The physical process in 

 obedience to which fluids pass from cell to cell, or through 

 any permeable membrane, has been named endosmosis 

 and exosmosis. The first is given to the inward flow and 

 the other to the outward. These names were applied by 

 H. J. Dutrochet, an eminent French physiologist, who 

 wrote several valuable treatises on animal and vegetable 

 physiology, published in Paris between 1824 and 1837, 

 and since his time the above terms have been in common 

 use. The explanation of this process of transudation is, 

 that liquids of different density, placed on opposite sides 

 of a permeable membrane, are naturally attracted or flow 

 towards each other, and sooner or later become inter- 

 mingled. The thinnest liquid will flow towards and into 

 the thicker, and this movement is called endosmose, 

 while at the same time a much smaller amount of tlie 

 thicker will flow out into the thinner (exosmose), until 

 both become of equal density. A linen or silk bag, filled 

 with honey or thick syrup, and suspended in a pail of water 

 will furnish a good illustration of the movements of fluids 

 by transudation, for while the water will flow in, some of 

 the honey will be dissolved, thinned, and then flow out, 

 this process continuing until the entire liquid becomes 

 merely honey-flavored or sweetened water, and of the 

 same density throughout. The same kind of interchange. 



