I 3 8 BOTANY FOR BEGINNERS CHAP. 



there is a little space between them, and dip them into the liquid in the 

 tumbler. Note 



(i) The coloured liquid rises between the slips of glass. 



(ii) The height to which it rises will depend upon the width of the 

 opening between the slips. The greater the distance between the slips 

 of glass the shorter the column of liquid ; and the nearer they are together 

 the higher the coloured water will rise. 



(iii) The liquid rises by capillary attraction. 



The finer the particles in the soil the more water will be held 

 by it. The interspaces between the particles of the soil form so 

 many capillary tubes, up which the water rises, and by which it 

 is held. 



Absorption. The root-hairs make their way into the 

 interspaces, and come into close contact with the water round 

 the particles. The water gradually diffuses through the thin 

 cell-wall of the root-hair, or uncuticularised portion of the root ; 

 it thus reaches the interior of the root-hair and eventually passes 

 up into the plant, while a little acid sap diffuses out from the 

 cell into the soil. That plants do take in water by their roots 

 can be shown by growing a plant in water in which a little eosin 

 has been dissolved. The solution of eosin is taken in. 

 the roots being stained internally for a considerable distance 

 above the water. Only those substances in the soil which are 

 soluble in water can be taken in by the plant. This can be 

 shown by the following experiments. 



EXPT. 124. Put a little powdered eosin in water, and place the roots 

 of an actively growing plant so that they dip into the solution. Leave 

 the roots of the plant in the solution for several hours, and examine in 

 the following way : 



(i) Examine the root ; it will be coloured externally for a short 

 distance above where the water stood. 



(ii) Cut a transverse section of the root and mount it in glycerine. 

 Examine under the low power of the microscope ; the section is seen to 

 be stained right through. 



(iii) This shows that the soluble eosin can pass along with the water 

 through the cell-walls. 



EXPT. 125. Place a little powdered carmine in water, and place the 

 roots of an actively growing plant so that they dip into the mixture. 

 Note 



(i) The carmine does not dissolve, but remains suspended in the water, 



(ii) Cut a transverse section of the root and mount in glycerine. 

 Examine with the low power of the microscope. Observe the carmine 

 has not passed into the plant, for the section is not coloured. 



(iii) It is only the soluble constituents which can pass through the 

 cell-wall along with the water. 



