CH. Ill] ROOT-HATRS. 47 



show that each hair is an external cell elongated by 

 growth at right angles to the surface of the root. When 



FIG. 19. 



MUSTABD SEEDLING, 



showing the cotyledons (C), and the root covered in its older 

 part by root-hairs (R). 



it is understood that each of the innumerable rootlets of 

 a well-grown plant bears root-hairs, it will be realised 

 how enormously the surface of the root is multiplied. 

 The nature of the contact between the plant and the soil 

 is extremely close ; if a plant is removed from the soil 

 and examined under the microscope it can be seen how 

 the root-hairs press against, even to some extent wrap 

 round and adhere to, minute particles. The adhesion of 

 the root-hairs to the soil can be simply demonstrated by 

 pulling a seedling up from loose soil, when it presents the 

 appearance shown in fig. 20. The apical region of the 

 root comes up clean and bare, while the basal region is 

 shaggy with its coat of earthy particles. In older plants 

 a further fact may be demonstrated in the same way. 

 In these the basal, as well as the apical part of the root 

 is bare, because the root-hairs are short-lived organs, and 

 where they are dead the root does not retain its envelope 

 of soil. 



I have spoken of the root absorbing water, but it must 



