PLANT PHYSIOLOGY AS RELATED TO PRUNING V 



allowing the seedlings to grow a few days between sheets 

 of white blotting paper. When so grown they are more 

 or less straight, but when grown in the soil they are 

 much contorted because of the contact of soil particles. 

 11. Root hairs are usually most numerous on plants 

 growing in soil that is dry, and least in that which is 

 saturated with water. Also, when the waier supply de- 



_J_^,^ ^_Jw_ 



FIG. 7— ROOT 



HAIR GREATLY 



MAGNIFIED 



FIG. R— ROOT TIP MUCH 



MAGNIFIED 

 epidermis; h, cortex; c, ple- 

 rome; d, root cap. 



minishes they become more numerous ; and when it be- 

 comes wet, less abundant. Plants grown in wet soil and 

 then transplanted to soil much drier will suffer severely 

 unless watered. Often they will die because they cannot 

 develop root hairs fast enough to supply the loss of mois- 

 ture by transpiration from the leaves. 



This finds a specially important application in the prun- 

 ing of nursery stock at transplanting time ; the tops of 

 the plants must be cut back to balance the unavoidable 

 loss of roots due to digging. (Chapter IX.) It may be 

 proved very simply by the following experiment : Sow 

 some cabbage or lettuce seeds in a flat filled with soil of 

 uniform quality. When the plants have two or three 

 leaves aiul are large enough to prick out, divide the most 



