THE WORK OF ROOTS 103 



root would have to be from fifty to seventy -five times 

 thicker, i. e., from an inch up to five or six inches 

 in diameter. 



How do the roots (and especially root-hairs) manage 

 the absorption of water from the soil? Do they find 

 themselves surrounded by water ? Tie over the bottom 

 of a lamp-chimney (a student-lamp chimney, size No. 

 1 is very good) a piece of cheese-cloth; fill the chim- 

 ney with soil that is moist enough to allow good plant- 

 growth, and place it in a' pan. Pour water into the 

 pan and notice its rise in the soil. Are the spaces 

 between the soil -particles filled with air or with water 

 at the beginning of the experiment 1 Take some more 

 moist soil, and spread it out on a thin layer on a 

 piece of paper. Notice the glistening appearance of 

 each particle; as the soil dries this disappears and 

 the particles become dull in appearance ; why ? If 

 fine gravel is used, the whole process is very easily 

 seen. It appears, then, that in moist soil the water 

 is in the form of thin films around each particle and 

 the spaces between these particles are filled with air; 

 only in wet soil are these spaces more or less filled 

 with water. 



In order to understand how the root absorbs water 

 from the soil, we must understand what the soil is. 

 Let us, therefore, take up the question, Of what is the 

 soil composed? 1 Take a handful of earth, rub it up 



i See King: "The Soil." 



