10 PRODUCTIVE FARMING 



Exercise. — Sap Channels in Stems. — Put the stems of 

 fresh plants into water colored with red ink. After a few 

 hours cut off the stems and notice the stained places on the 

 cut surface. Use for this exercise some woody stems, as 

 willow, and others like celery or rhubarb, golden-rod, corn, 

 tall grass, or other convenient plants. 



The different ways in which the stems of various plants 

 hold the leaves up to the light and air are interesting. Vines 

 do this by climbing upon objects which they may find near 

 them. Trees have rigid stems which hold the leaves high 

 in the air. Those growing in dense forest clumps are taller 

 and more slender than those growing in open places where 

 there is plenty of light. This is also true of corn-stalks planted 

 close or far apart. 



The leaves of the plant have much work to do. They 

 secure substances from the air, chiefly carbon dioxide, and 

 change it into forms of food that will build up the plant or 

 produce growth. The leaves also permit the escape of water 

 from the plant into the air. Water is taken up by the roots, 

 not by the leaves. There are large amounts of water given 

 off by the leaves during the growth of the plants. 



Exercise. — Plants Absorb Moisture. — Get the material 

 shown in Fig. 3a. After the corn or other plant is a few 

 inches high, start the experiment. Have the water line 

 marked on the lard pails one inch above the bottom of the 

 pots. Each day fill the water up to the mark, and record 

 the amount required for each pail in two weeks. If the one 

 with the growing plant requires the most, where has the 

 extra water gone to ? 



Exercise. — Moisture from Leaves. — Arrange an exper- 

 iment as shown in Fig. 36. The moisture which escapes 

 from the leaves will partly be condensed on the inside of the 

 inverted glass, and may be seen in fine mist or drops. 



Leaf Structure. — Fig. 4 shows the cut edge of a leaf. 

 Between the upper and lower surfaces of the leaf there are 



