PHYSIOLOGICAL PROCESSES IN PLANTS 



79 



Observations. 1. What has happened to the tacks ? 



2. Examine some sand with a hand lens. Also examine 

 some soil in the same way. What do you observe ? 



Conclusions. 1. Could other minerals be affected in the 

 same way as the iron ? What would be the result ? 



2. Show how iron might become a part of the soil. 



3. How does freezing and thawing affect soil and rock? 



4. What happens when glaciers grind rock against rock ? 



5. What happens when waves dash against rocks ? When 

 water runs swiftly over rocks ? 



6. Summarize the various sources of mineral matter in soil. 



2. ORGANIC MATTER 



Observation. Examine some loam and soil collected from 

 beneath trees. 



Conclusion. What else evidently constitutes part of the 



soil ? Reasons. 



b. Kinds of Soil 



Method. Take a pound of rich mold from under forest 

 trees, a like amount of rich loam from beneath this mold 

 (black soil), and the same amount from a barren roadside or 

 field. Dry them. Place them on a pie tin or piece of sheet 

 iron, and heat them red hot over a gas stove or coal fire until 

 all that will burn seems to be burned up. Re weigh each sam- 

 ple. Put what remains in bottles and give them to the school 

 museum, if you desire, after labeling them. 



Observations. 1. Tabulate results as follows : 



2. Note the final appearance of the samples. 

 Conclusions. 1. What do the losses in weight indicate ? 



