PLANT PHYSIOLOGY AS RELATED TO PRUNING 



11 



tionately the greater as the fineness of the particles and 

 the quantity of organic matter in the soil increase. An idea 

 of the extent of the root systems of cultivated plants 

 may be gained from the statement that a full-grown sun- 

 flower will fill almost a full cubic yard of soil with its 

 r(.)ot system. Such an enormous water-absorbing area is 

 necessary because other 

 parts of the plant (in agri- 

 cultural plants, at least,) 

 are not fitted or at best are 

 poorly fitted for absorbing 

 water. 



Even leaves which are 

 supposed to absorb water 

 when wilted by rain and 

 dew are much less able to 

 do this than is popularly 

 supposed. Yes, leaves 

 wilted by hot weather 

 cjuickly become turgid after 

 a shower, but this is far less 

 due to the water on sur- 

 faces than to the reduction 

 of transpiration in the 

 cooler, moister air and to 

 the increased supply of 

 water which the roots can 

 draw upon. Leaves of some 

 plants, however, are able to 

 take up water much more 

 readily than others, but 

 these are such as do not 

 concern the subject of 

 pruning. 



13. Osmosis and diffusion of water account for passage 

 of water from the soil through the root hairs and upward 



FIG. 10- 



■HOVV NURSERY TREES 

 ARE DUG 



Dotted line shows diagratnmatically 

 where roots are cut; a, what the pur- 

 chaser gets; bj what is left in the soil. 



