CHAPTER III 



GROWTH OF ROOTS, STEMS, AND LEAVES 



Do all parts of the root continue growing as it pushes down 

 into the soil? 



To answer this we must have the roots where we can 

 examine them. Let us take a fruit-can rim. Make holes 

 about half an inch apart around the edges, and weave strong 

 cord across above and below. Fill with chopped moss or 

 cotton wool, in which place germinating bean or pumpkin 

 seeds, and suspend in an inverted flower-pot over a saucer 

 of water. When the roots have grown below the germinator 

 about an inch and a half, mark off equal distances on the 

 roots with ink (waterproof ink is better). Place the germinator 

 under cover, and observe the next day. The spaces toward 

 the upper end nearest the seed will be the same distance apart 

 they were the day before. The root has not grown there nor 

 at the tip. Growth in length is greatest just at the back of 

 the tip. 



In a similar way examine the growth of stem and leaves. 

 Mark off equal distances as before ; they may be a little 

 farther apart on the stem. The place on a stem from which 

 leaves are given off is called a node. The part between two 

 nodes is called an internode. Notice that the stem grows 

 both below and above each internode, but the greatest elonga- 

 tion is in the upper half of an internode. How does a leaf 

 become larger ? 



Now compare the results with the stem growth of mono- 

 cotyledons. 



Place Zea mais seedlings where they are warm. When 

 the first blade is about two inches above ground, or as soon 



