194 NATURE-STUDY REVIEW [14:5— May, 1918 



Describe the feet. (Claws and pads). Use? (Crawling and 

 clinging) . How many pairs of wings does this insect have ? (Two) . 

 Note which wings are used in flying? (Inner). In what way 

 are they adapted for flying? (Light and gauzy). Describe the 

 outer wings. (Hard and shell-like). What do you infer is their 

 use? (Protection to delicate under- wings) . Pick up a beetle 

 and note how it "plays possum." When one brushes against a 

 potato plant the adult insects drop to the ground and "play 

 possum". What is the advantage of this habit? Hold the insect 

 rather firmly. What is another method of protection? (Acrid 

 secretion) . 



The orange colored eggs are laid on the underside of the leaves. 

 Advantage? 



The potato-beetle was a native of Colorado where it lived on 

 a wild plant of the nightshade family. 



VI. Conservation of Moisture 

 This lesson should precede the cultivation of the potato crop. 

 Experiment i. Devise a rack to hold four lamp chimneys in 

 a vertical position. Tie a piece of cloth over the bottom of each 

 and fill within three inches of the top with gravel, sand, clay, and 

 loam, respectively. Pour the same amount of water into each 

 chimney and note the time it takes each soil to absorb the water. 

 Which allows the water to pass through most quickly? Which 

 soil should we add to a garden that loses its moisture too rapidly ? 

 What soil should we mix with garden soil that does not absorb 

 water readily? The force which causes the moisture to go down- 

 ward is called gravity. In heavy soils plant potatoes about 

 three inches deep and in light loose soil four to five inches deep. 

 Why? 



Experiment 2. Pack the soils in the lamp chimneys rather 

 firmly and add a loose dry layer of the same kind of soil on top. 

 Let the lower ends of the chimneys in a pan of water. Note the 

 rate at which the water passes upward in each soil. Compare 

 the rate at which the moisture passes upward in the packed soil 

 and in the loose surface soil. This upward movement of the 

 water is due to capillary attraction. Which would you expect 

 to be more important for the plant, gravitational water or capil- 

 lary water? This experiment shows how tillage will conserve 

 capillary water. Explain. The surface layer is called a mulch 



