ROOTS AND THEIR WORK 93 



a furnace until you feel sure that all organic matter is burned up. Then re- 

 weigh each and put the soil into three bottles, giving the weight before and 

 after burning in each case. Professor Hodge (see Nature Study and Life, 

 page 380) tried this experiment, and found that when each lot originally 

 weighed 100 grams, the forest leaf mold in burning lost 78 grams, the forest 

 loam lost 11 grams, while the barren soil lost only 1 gram. What results do 

 you get from your experiment? 



The Root Hairs take more than Water out of the Soil. — If a 



root containing a fringe of root hairs is washed off carefully, it 

 will be found to have little particles of soil still clinging to it. 

 Examined under the microscope, these particles of soil seem to 

 be fastened to the root hair. The following experiment explains 

 what the root hairs do to the soil surrounding them. 



Grow a number of seedlings in a tumbler between blotting paper and 

 the edge of the glass or in a pocket garden. Place a sheet of blue ' litmus 

 paper so that the root will grow against it. Does a change of color take 

 place near the root hairs? 



Acid Reaction of Root Hairs. — The change of color of the 

 litmus paper from a blue to red shows us that the growing root 

 hairs have a decidedly acid reaction. Thus some mineral matters 

 which otherwise could not be taken into the root hair are dis- 

 solved by the action of the acid. Lime (oxide of calcium), for 

 instance, is such a mineral. The minerals that the root hairs 

 take in with the soil water are calcium, potassium, iron, silicon, 

 and other elements, in very small quantities. If radish or other 

 seedlings be grown in moist, rich soil, and then removed when 

 but an inch in height, the soil will be found to cling to the root 

 hairs. In fact, the surface of the root hair often almost incloses 

 tiny particles of soil, the acid given out literally eating away the 

 soil particles thus inclosed. 



The proportion of each of these mineral materials is very small 

 compared with the water in which they are found. A very great 

 amount of water must be taken up by the roots in order that 

 the plant may get the needed amount of mineral matter with 

 which to build its protoplasm. We also find that some mineral 



1 The blue litmus paper contains a vegetable material which turns red in the 

 presence of an acid. Red litmus paper changes back from red to blue when an 

 alkaline medium is present, ^^llen a substance will not change either red or blue 

 litmus paper, it is said to be neutral. 



