68 THE BEGINNER'S GARDEN BOOK 



water. Partly fill the thistle-tube with our strong solu- 

 tion of salt, and put it, large end down, in the bottle, 

 so that the top of the salt solution stands at the top of 

 the water. In a couple of hours the salt solution will 

 be seen to be rising above the water, and after a while it 

 will even be pushed out of the top of the tube. 



If we use molasses instead of salt, the contrast of colors 

 will show the result plainly. 



This seems to show that a lighter liquid will force its way 

 into a heavier liquid, even passing through a membrane first. 

 This is called osmosis. To partly test this, though without 

 a membrane that we can see, let us take some fresh slices 

 of potato, 1 drop some of them into water, and some into our 

 salt solution. At the end of an hour take them out. Those 

 taken from water will be stiff and crisp, those from the salt 

 will be soft and wilted. The water has passed into the 

 potato, where the sap is heavier still. But the sap has 

 passed from the other slices into the heavy solution of salt. 



Now we can see clearly enough how water passes from the 

 soil, through the skin of the roots, into the plant. As we 

 shall presently show, soil water has substances dissolved in 

 it. Once in the plant, what does the soil water do ? 



We can test this by dropping into a tumbler half full of 

 water, a spoonful of red ink. Into this put any white flower, 

 which should be fresh, with its stem freshly cut. It should 

 best be cut with a sharp knife, so as not to bruise the fibers. 

 On watching, we shall see the red water slowly pass up into 

 the flower, until it has entirely colored it. By such simple 

 means we can easily make what cannot grow in the garden, 

 a blue rose. We can try the same experiment with a tender 

 leaf, and can fill it with red or blue sap. 



The soil water therefore passes upward from the roots to 



1 The membranes here are the walls of the invisible cells. 



