GETTING ESTABLISHED 85 



upon the latter a funnel closed at the bottom with 

 a stopper; into this pour shot until the spring is com- 

 pressed to the same point as it was at the end of the 

 experiment. The weight of the funnel with the con- 

 tained shot gives the pressure exerted by the root. 



By preventing the root from bending, as suggested 

 on page 76, we could obtain much larger pressures. 

 Such a condition of things would occur naturally only 

 in a very firm soil. 



Another way to roughly test the power of the root 

 to penetrate the soil is to use a box with a bottom of 

 wire netting (the meshes being about five-eighths of an 

 inch square) . On the netting place cloths of various 

 thicknesses, tin-foil, slices of potato, or anything else 

 that the class may suggest. Fill the box with earth 

 and plant the seeds ; it may be easily observed if the 

 roots are able to penetrate any of these 

 objects; for this purpose hang the box 

 at a convenient height. 



What part of the root develops the 

 energy necessary for such strong growth ? 

 Remove some roots which are growing 

 in moist air (as shown in Fig. 78). 

 Mark them in the same way as you have 71. Root marked in 



,-,.-, , /TT^* '-1\ order to determine 



already marked the stem (.big. <1). the region of great- 

 Remove only one root at a time, mark ^^ ^""^ 

 it and place it as quickly as possible in water, where 

 it will continue to grow. Strong roots, such as those 



