128 AGRONOMY 



PRACTICAL EXERCISES 



1. Visit the nearest hothouse and note the character of the tropical 

 perennials that require great heat for growth. 



2. Ascertain from the nearest weather observer, or from farmers who 

 have kept records, the average date of the last killing frost in spring 

 and the earliest killing frost in autumn. How many days of growing 

 weather does this give you ? Find the date of the latest recorded spring 

 frost and the date of the earliest autumn frost. How many days from 

 frost to frost ? How does this compare with the average ? 



3. Into a bright tin cup, nearly filled with water, drop pieces of ice 

 one by one, stirring the mixture with a thermometer. When moisture 

 begins to appear on the outside of the tin cup, the thermometer will 

 register the dew point. Where is the dew point higher, in the school- 

 room or in a sheltered place outside ? In which place does the air hold 

 the more moisture ? 



4. Find a place where a board, paper, or other object has been lying 

 on the grass for a few days. Remove it and account for the appearance 

 of the grass underneath. 



5. Examine potatoes or other plants that have grown in a cellar or 

 other dark place. Explain the appearance of the plants. 



6. Make lath screens for use in the garden later, or draw plans to 

 scale for a lath house to be constructed in the garden for growing the 

 shade plants. 



References 



Dryer, "Lessons in Physical Geography." 

 Goff, "Principles of Plant Culture." 

 Salisbury, " Physiography." 



Farmers' Bulletin 



104. Notes on Frost. 



Weather Bureau 



311. Climate ; its Physical Basis and Controlling Factors. 



