22 



THE BOOK OF NATURE STUDY 



To show that substances must be in a state of solution, in 

 order that they may be absorbed, the following experiment 

 should be tried. Place a white narcissus in a tumbler containing 

 red ink and water. The solution passes up through the stalk of 

 the flower and colours its petals pink. Compare with this a 

 narcissus placed in carmine and water. The dye does not find 

 its way into the petals, for carmine does not dissolve in water. 



It is the root-hairs on the roots that absorb water and the 

 salts it contains. If seedlings are grown in sand, then taken 

 up when the roots are some inches in length, that part of the 

 root which has root-hairs will be covered with particles of sand. 

 The best way of seeing the root-hairs is to shake the seedling in 

 water, the sand comes off and the hairs are seen glistening in 

 the water. 



A seedling of wheat grown in soil and uprooted is shown. 

 The root-hairs are covered with particles of soil. (See Fig. 14.) 

 It is for this reason that in transplanting, it is most important 

 not to injure the tips of the roots behind which the root-hairs 

 are situated. If the soil is in a hard and dry condition, and the 

 plant is roughly pulled up out of the soil, the roots are almost 

 sure to be torn off in the operation. In such a case as this the 

 ground should be thoroughly watered, the soil 

 loosened with a fork or trowel, before the plant 

 is taken out to be transplanted. Special care 

 has to be taken with tap-roots, as it is very 

 easy to break the tip by rough pulling. For 

 this reason root crops, such as carrots, turnips, 

 radishes, are seldom transplanted. 



In Fig. 10, root-hairs are seen projecting 

 from the surface of the primary root of 

 FIG. io. Root-hairs of barley. Each consists of one long cell, with 

 very delicate cell walls. The structure of 

 the cells can only be seen with the aid of a 

 microscope. 



The work of the root-hair is to absorb food-material. The 

 water with salts in solution enters through the cell wall, which 

 is permeable. This is due to the fact that the contents of the 

 cell are different in density from the water with salts in solution. 



barley projecting 

 from surface of pri- 

 mary root. 



