120 WHY DO SEEDS GERMINATE? 



a bean is thus shown to be well supplied with nourishment until 

 it is able to take care of itself. In this respect it is somewhat like 

 a young animal within the egg, such as a bird or fish. All of our 

 cereal foods are made from seeds or grains that contain proteins, 

 carbohydrates, and oils. Seeds also contain water and mineral 

 matter, as can be shown by simple experiments. 



Self-Testing Exercise 



(1) solution is used to (2) for the presence of 



starch. If the (3) tested turns dark (4) or (5) > 



we know that starch is present. Oil is known by the presence of a 



(6) spot when the (7) is heated on (8). To 



test for protein we add (9) (10) to the substance : if 



it turns (11) (12), it is an indication that (13) 



is present. If (14) (15) is then added to the sub- 

 stance and it turns a deep (16) color, we may be sure that 



it is a protein. 



PROBLEM III. WHAT FACTORS ARE NECESSARY TO 

 AWAKEN THE EMBRYO WITHIN THE SEED? 



Demonstration 4. To show how much water is needed for the 

 germinating of peas. 



Materials. Soaked and dry peas, sawdust, cups. 



Method. Place an equal amount of moist sawdust in the bottom of 

 each of two cups. 1 Put ten soaked peas in each. In a third cup con- 

 taining dry sawdust put ten dry peas. Keep the seeds in one cup 

 partially covered with water, those in the second slightly moistened, and 

 those in the third dry. Keep the cups covered in a moderately warm 

 place. Examine them daily for four days. Tabulate your results. 



Conclusion. Which amount of water seems best for germination ? 

 Give your reasons. 



How much water does a seed need in order to germinate? 



The exact amount of water which is most favorable for the ger- 

 mination of a seed can be determined only by careful experiment. 



1 Pupils performing this or any other experiments must remember that the suc- 

 cess of an experiment depends upon the accuracy with which it is performed and 

 the exclusion of all factors from the experiment except the one which they are try- 

 ing to prove. For example, in the experiment on the effect of different amounts of 

 moisture, all the other factors — temperature, light, food, etc. — must be the same 

 in each of the three cups ; the only variable factor being moisture. 



