ROOTS AND THEIR WORK 



83 



A pocket germinator, in which the roots of the barley 

 seedlings show a turning in response to gravity. The 

 germinator was originally turned 180° from its present 

 position. 



place on it some well- 

 soaked radish or mustard 

 seeds or grains of barley, 

 and cover it with the 

 other glass. The whole 

 box thus made should be 

 bound together with bi- 

 cycle tape. Seeds will 

 germinate in this box, and 

 with care may live for 

 two weeks or more. 



Influence of Gravity. 

 — We are all familiar 

 with the fact that the 

 force we call gravity 

 influences life upon this earth to a great degree. Might gravity 

 act on the growing root ? This question may be answered by the 

 following simple experiment: 



Place your 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 the 

 box at right angles to the first position. Allow it to remain for one day 



^_, undisturbed, and then examine it. The roots 

 will be found to have turned in response to 

 the change in position. In what part of the 

 root does the change take place? What 

 part of the growing root is most easily in- 

 fluenced by the force of gravity? Make a 

 series of drawings to illustrate this experi- 

 ment. This experiment seems to indicate that 

 the roots are influenced to grow downward by 

 the force we call gravity. 



Experiments to determine Influence 

 of Moisture on a Growing Root. — 



The objection might well be interposed 

 that the roots in the pocket garden 

 grew downward after water. This is 

 unlikely, however, as the air in the 

 germinator is saturated with moisture. 

 That moisture has an influence on the 

 growing root is easily proved. 



Revolve this figure in the direc- 

 tion of the arrows to see if the 

 roots of the radish respond to 

 gravity. 



Plant bird seed or the seed of mustard or radish in the under side of a 

 sponge, which should be kept wet, and may be suspended by a string under 

 a bell jar in the schoolroom window. Note whether the roots leave the 

 sponge to grow downward, or if the moisture in the sponge is suflBcient to 

 counterbalance the force of gravity. 



