46 . .1 UNIT IN AGRICULTURE 



Fill seven four-inch flower pots with clean sand. Number the pots 

 and place plant food in each as follows: 



No. 1. Nothing. 



No. 2. Ten grains lime. 



No. 3. Ten grams lime and one gram potassium chloride. 



No. 4. Ten grams lime and one gram acid phosphate. 



No. 5. Ten grams lime and one gram sodium nitrate. 



No. 6. Ten grams lime ;m<l <>nc gram each of the compounds 

 used in Nos. 3, 4, 5. 



No. 7. About one-half pint of manure. 



Mix 'the materials in each pot, then plant five kernels of wheat in 

 each. Record the growth of the plants from day to day, noting dif- 

 ferences in color and amount of growth. Let the plants grow until 

 the differences are clearly apparent. 

 Ex. 46. Air-Derived and Soil-Derived Elements. 



Select a dry plant or a piece of dry wood. Weigh it carefully. 

 Now burn it and weigh the ashes. What per cent of the plant burned ? 

 This method gives a fair approximation of the amount of materials 

 derived from the air and amount of materials derived from the soil. 

 Review the following questions: 



Will any seed germinate in a perfectly dry soil? Will any plant 

 grow without some moisture ? Why is there so little vegetation in the 

 desert? What is a desert? What is meant by a drouth? What 

 would be the effects on this country of a total cessation of rainfall? 



Ex. 47. Bacteria and Molds. 



Material : three test tubes, cotton, boiled potato, fruit or apple 

 sauce, three apples, one partly decayed. 



Fill each tube about one-third full of apple sauce. Plug each 

 with cotton. Set one aside. Put the other two into a pail of water 

 and boil for half an hour. After boiling, set one tube aside with the 

 cotton undisturbed. Take the cotton from the third tube, leave it 

 out half an hour or more, and then put it in again. Leave these for 

 a few days, note what happens and account for different results. Is 



