Roots 1 1 1 



for their use. The "loamy soil" which a farmer loves 

 contains from forty to seventy per cent of sand. 



Here, again, we see the great usefulness of earth- 

 worms. In sand they, like the roots, can make their way 

 so easily that they have little need to remove the soil by 

 swallowing it, the only means at their disposal. But in a 

 stiffer soil they are obliged to do this, and thus they let in 

 both air and water, to the great advantage of the plants, 

 while they also spare the roots much labor by preparing 

 for them airy passages, down which they can run with ease. 



But though roots take advantage of these ready-made 

 channels, and are evidently all the better for them, they 

 do not let go their hold on the soil, but keep a close grasp 

 of it, lining the worm-burrows with thread-Hke fibers, 

 which cling fast to the sides. 



Roots coming in contact with a piece of limestone will 

 leave upon it a perfect impression of themselves, even to 

 the hairs with which they are fringed, showing how, like 

 the lichens, they have eaten their way into the solid sub- 

 stance. 



How do they do it.? We can hardly do more than 

 conjecture; but it seems probable that the acid in the 

 roots acts much as acid contained in a bladder would. If 

 a glass tube is filled with water made slightly acid with 

 vinegar, and then covered with a piece of moistened 

 bladder strained tightly over the mouth, and in contact 

 with the liquid, this will represent the root, though the 

 resemblance would, of course, be closer if the tube itself 

 were of bladder. This, however, seems to be the only 

 practicable way of trying the experiment. The acid is 

 very weak, as the acid in the roots is weak; but if salts, 

 such as phosphate of lime, and others found in the soil. 



