114 



EXPERIMENTS WITH PLANTS 



has the larger particles ; the larger spaces ; does this 

 explain the ma.tter! An inch of rain is said to pene- 

 trate four inches in clayey soil and six to 

 eight inches in sandy soil. What do you 

 think of this statement? Does air in the 

 soil hinder percolation ? 



What becomes of the rain-water which 

 percolates down through the soil ; is any of 

 it drawn back up again as the surface dries? 

 Prepare a bent tube as shown in Fig. 86, 

 one arm being about eighteen inches long 

 measuring ^the ^^ ^ e Q^gj. about four inches. Push a 



ration from a 



saturated soil, little wet cotton nearly to 

 the bottom of the longer arm; fill 

 this with clay; fill the longer arm of 

 a similar tube with sand. Attach a 

 funnel, as shown in Fig. 87, and pour 

 water upon the soil in each tube until 

 the shorter arm of the tube is partly 

 filled; when it stops rising, remove 

 the funnel and pour a few drops of 

 oil on the surface of the water in the 

 shorter arm of the tube, to prevent 

 evaporation. Mark accurately on a 

 strip of paper gummed to the tube 

 the height of the water -column (it 

 should be about the same in both ST. Method of supplying 



.-, v Tfji / -n -\ water to the apparatus 



tubes) . It the water rails in the shown in Pig . 86 . 



