HIE PIIYSIOLOCY OF PI.ASTS 279 



iiicuibrancs, h.uiiiL; the same pi')|;ci't)' as the 

 nicinbianc \\c placed 011 the lamp sharle ; inside 

 the root hairs there exists hea\y dense cell sap, 

 outside are the films of hygroscopic water con- 

 taining (dissolved; inorganic salts, and this water 

 passes in through the inembranc of the root, whilst 

 a very little of the cell sap passes out into the soil, 

 the (|uantit\- passing in being greatl)' in excess of 

 that which esca])es. 



When once the crude water of the soil is inside, 

 it is soon passed along to the stem and leaves b\- 

 the pressure of more water coming in, and by what 

 is called capillary poiocr ; this power we may easd)- 

 sec if we dip a fine tube into water, when at once 

 the water will rise up some distance into the tube. 

 I have pointed out that plant food is gaseous as 

 well as aqueous. 



Ox\\gen is absorl)ed b}' the root \er\- freel\" from 

 the soil, and, tlierefore, farmers and gardeners 

 frequentl}' plough and stir the soil of fields and 

 gardens so that the roots ma}- obtain a suppK" of 

 this needful gas. 



Let us now endeavour to see how the gaseous 

 fo(jd is taken into the plant. In order to do so 



