122 WHY DO SEEDS GERMINATE? 



Self-Testing Exercise 



In order for seeds to germinate they need a (1) supply of 



(2), a certain degree of (3), and (4). The 



amount of (5) required for germination varies with the kind 



of ;. . (6). If too much (7) is used, some seeds will 



(8) or decay. 



PROBLEM IV. WHAT BECOMES OF THE PARTS OF THE 

 EMBRYO DURING ITS GROWTH INTO A YOUNG PLANT? 



Germination. If you plant a number of soaked kidney beans 

 in damp soil or sawdust and at the end of each day remove one, 

 you will be able to obtain a complete record of the growth of the' 

 kidney bean. The first signs of germination are the breaking of 



Stages in the growth of a bean. Note the direction of growth in the root. How does the cotyle- 

 don get out of the ground ? What has happened to the hypocotyl in the right-hand figure ? 



the testa and the pushing outward of the hypocotyl to form the 

 first root which grows downward. A later stage shows the 

 hypocotyl forming an arch and dragging the bulky cotyledons 

 after it. The stem, as soon as it is released from the ground, 

 straightens up. The cotyledons open, and between them the 



