52 SEEDS 



Suggestion. Repeat this experiment, using four bottles, 

 filling one pair with fresh live seeds and the other pair with 

 seeds which have previously been killed by heat in an oven. 

 Fill one of each pair with water as before. Cork them and 

 set them away to await results. 



Does expansion occur equally in all preparations? 



Is the result due to mechanical or to physiological causes ? 



Give reasons for your answer. 



37. SEEDS EXERT PRESSURE 



Object. Same as in Experiment 36. 



Method. Repeat Experiment 36, using flowerpots, bricks, 

 and wire as follows : Fill a flowerpot with dry seeds. Place 

 a brick over the top and wire it on firmly. Then immerse 

 the whole in a pail of water and leave it overnight. 



Lift the flowerpot carefully out of the water and note 

 the result. If the brick has been fastened down firmly, 

 there will be something worth seeing. How can you account 

 for the result ? 



Query. Is this power of exerting force of any use to 

 the seed in getting started under the ground? 



Note. A piece of board may be used instead of a brick in this 

 experiment. In this case the board may be bent and the flower- 

 pot not broken. 



An embryo is an immature or undeveloped plant or animal. 

 Every seed contains such a plant surrounded by one or more 

 coverings called seed coats, which serve to protect it. 



There is also laid up within the seed a quantity of food 

 for the use of the embryo when it begins to grow. This 

 food is sufficient to nourish the plant until it has developed 

 root and leaf surface enough to manufacture food for itself. 



