THE WORK OF ROOTS 



99 



roots turning in the same direction, instead of which 

 they radiate in all directions from the main root; and 

 not only so, but roots from neighboring plants cross 

 each other growing in opposite directions. Is it, 

 then, gravity ? We may test this very simply. 

 When the side roots have grown some distance, tip up 

 the box, as in Fig. 81. Carefully mark on the glass 

 the position of each side root; mark with especial care 

 the position of the tips. Leave the box undisturbed 

 and make daily observations. 

 Do the l side roots change 

 their direction ? Do the 

 rootlets which spring from 

 them change theirs ? 



As we watch the roots 

 growing along inside the 

 glass, we may occasionally 

 see them encounter small 

 sticks or stones or other ob- 

 stacles ; what do they do 

 then? Obstacles may be pro- 

 vided in abundance by 

 fastening small pebbles or 

 blocks of wood to the glass 

 with sealing-wax before put- 

 ting the soil in the box (Fig. 

 80) , or to the sides of a glass 



i / 171- or\ T\ 82. Modification of the apuaratus 



funnel ias m Fig. 82). Do shown in Fig . 80 . 



