ROOTS 



141 



Place the pocket garden on one edge, and allow the seeds to germinate 

 until the root has grown to a length of about half an inch. Then turn it 

 at right angles to the first position and allow it to remain for one day 

 undisturbed. Turn it again. In a day or so examine it. Describe your 

 results. 



The part of the root near the growing point is the one most 

 sensitive to the change. This experiment indicates that the roots 

 are influenced to 

 grow downward by 

 the force of gravity 

 and that the grow- 

 ing point is most 

 responsive to this 

 stimulus. 



primary 

 secondary- 



Demonstration 3. 

 Does water affect 

 the course taken by 

 roots ? 



Divide the in- 

 terior of a shallow 

 wooden box with 

 glass side into two 

 parts by a partition 

 with an opening in 

 it. Fill the box with 

 sawdust. Plant peas 

 and beans in the 

 sawdust on one side 

 of the partition, and 

 water them very 

 slightly, but keep the 

 other side of the box 

 well soaked. After 

 two weeks, take up 

 some of the seed- 

 lings and note the 

 position of the roots. 



Water a factor which determines the course taken by roots. 



Water, as well as the force of gravity, has much to do with the 

 direction taken by roots. If radish seeds germinate on the under 

 side of a moist sponge suspended in the air, their roots will turn 

 against gravity and cling to the wet surface of the sponge. Water 

 is always found below the surface of the ground, but sometimes 



taproot system fibro«*-ro«t, 



sveet clover- system of-vheat 



What is the length of the root system as compared with the height 

 of the adult plant in each case ? 



