v ANATOMY STUDY OF ROOTS 59 



quarter of a pound. Roots not only move in the direction of least 

 resistance, but also towards damp and away from dry soil. 



The use of these movements to the plant cannot be over- 

 estimated. If the root made its way through the soil in a 

 perfectly straight line, not half the favourable spots for food 

 would be touched ; the spiral or circular movements of the root 

 ensure its contact with the best sources of food in the soil. The 

 tip of the root is also very tender and liable to be injured, and 

 the movement from side to side enables it to find the path along 

 which there is least danger to the growing point. 



EXPT. 46. Take a few Beans or Peas and germinate them on damp 

 sawdust. When the radicle appears through the micropyle, turn the 

 seeds over so that the radicle points upwards. Under another radicle 

 place a piece of glass. Notice how the radicles act. 



EXPT. 47. Using the Beans or Peas germinated above, 



(i) Cut off the root-tip of a radicle, so as to separate it just above the 

 growing point. 



(ii) Place a piece of post card on one side of the tip of a radicle, and 

 on the other side a piece of tissue paper. This can be done by using a 

 solution of shellac. 



(iii) Cut slices from a few radicles, so as to remove a longitudinal 

 layer from one side. Great care must be taken not to fix the card too 

 far away from the tip or the radicle will turn towards the card, not 

 away from it. Make notes of the results. 



EXPT. 48. Replace one of the sides of a box with a piece of glass. 

 Fill up the box with alternating layers of sand, sawdust, clay, and peat. 

 Sow mustard seeds or the seeds of any quick growing plants. Cover up 

 the front of the box with a piece of cardboard. Keep the box warm 

 and damp. When the seed leaves are well up in the air, place the box 

 on a window sill. Remove the cardboard from day to day, to see how 

 the roots are placed against the glass. 



EXPT. 49. Take the bottom out of a box, and nail on in place of 

 the bottom a piece of wire netting with holes of about a quarter of an 

 inch in diameter. Fill the box up with soil, placing the largest particles 

 at the bottom. Grow plants as in Expt. 48. Hang the box up in a 

 window and keep the soil moist. Note 



(i) The roots will pass out through the wire netting. 



(ii) Many, if not all, will bend up and pass again into the box. This 

 shows that the radicle or roots like darkness better than light. In fact, 

 nearly all roots grow away from the light. 



SUMMARY. 



Roots can be divided into 



Primary roots. A primary root is produced when the radicle goes 

 on growing. Thus, all primary roots are produced by the elongation of 



