80 



PHYSIOLOGICAL PROCESSES IN PLANTS 



2. Which sort of soil is richest in organic matter? Inorganic 

 matter ? 



c. Water-retaining Ability of Soil 



Method. Take J pound each of gravel, sand, barren soil 

 (clay), rich loam, leaf mold, and T L- pound of dry leaves. 



B C D E F 



FIG. 18. Experiment to show kind of soil which best retains water. A, 

 gravel; , sand; C, barren soil; D, rich soil; E, leaf mold; F, dry leaves. 



Thoroughly dry before weighing. Now place the samples as 

 shown in Figure 18, shake them down, and slowly pour J pint 

 of water on each. 



Measure all that runs through and tabulate results as 

 follows : 



Observation. Amount of water left in soils. 



Conclusions. 1. In which sorts of soil would roots best get 

 their water supply ? 



2. Is the forest floor of leaves and loam of any importance 

 in retaining the water of rain or snow ? Explain. 



3. What would likely be the character of the water drained 

 from such forest floors ? 



4. What is indicated by muddy streams ? By the muddi- 

 ness of the Missouri River ? 



