THE PLANT IN ACTION. 247 



carelessly left in it, so this water of the soil, entering 

 by the spongioles and root-hairs, passes from cell to 

 cell, and along the vessels and fibres of which the 

 plant is composed. 



A second force, which aids in feeding plants, is 

 known as osmose. If you place any porous mem- 

 brane between two liquids of different density, a 

 movement of these liquids through the membrane 

 at once begins. Suppose that, on one side there is 

 syrup, and on the other pure water, there will be a 

 flow in both directions through the membrane ; the 

 water will become sweet, and the syrup will be di- 

 luted. But the amount of flow is much greater tow- 

 ard the syrup than toward the water, and, if the cir- 

 cumstances permit, the action will continue till the 

 liquids on the opposite sides are alike in density. 

 You may observe this effect in the cooking of ber- 

 ries, as currants, for instance. Here the outer mem- 

 brane, or skin, of the fruit is between its internal 

 watery juices and the syrup in which it is stewing. 

 This water passes outward, through the membrane, 

 into the syrup of the stew-pan, in much greater 

 quantities than the syrup passes inward, and so the 

 fruit shrivels. On the contrary, if you take dried 

 currants, in which the juices are concentrated, and 

 the fruit already shrivelled, and stew them in pure 

 water, an opposite action takes place. The berry 

 now receives more water than it loses, swells, and 

 assumes its natural shape. In both these cases the 

 principal movement is that of the pure or less dense 

 liquid toward the denser syrup. This is an example 

 of what is called osmotic action. 



Now, the cells of plants, like the dried fruit in 



