CHAPTER XI 



THE ABSORPTION AND MOVEMENT OF WATER IN THE 

 PLANT 



I 



Absorption of Water and Minerals. It is a well- 

 known fact that if plants are not supplied with water they cease 

 to grow ; they droop, wither, and die. All the 

 substances which a plant requires for its growth 

 are taken from the soil with the exception of 

 carbon^ and this, as we have seen, is obtained 

 from the air. That the roots are the organs 

 which take in water is shown by the experiments 

 in water culture. The parts of the roots active 

 in absorption are the rqpt-hairs, and the 

 uncuticularised portions of the younger 

 roots. Root-hairs are unicellular and thin- 

 walled, the walls being lined with protoplasm. 

 These root-hairs pass between the particles of 

 the soil, and by their intimate connection there- 

 with absorb water which contains minerals in 

 solution. Even in a dry soil there is a certain 

 amount of water round the particles, held there 

 by capillary attraction. This water may pass 

 from particle to particle by the same capillary 

 force. Capillary attraction similarly causes 

 water or tea to completely saturate a piece of sugar if one corner 

 is wetted ; it also determines the flow of oil up the wick of a lamp. 



EXPT. 123. Obtain two slips or pieces of window glass and a tumbler 

 partly filled with a coloured liquid. Place the pieces of glass so that 



FIG. 156. Tip of 

 root-hair, with 

 adhering parti- 

 cles of soil. 



(X2 4 0.) (S.) 



