PROBLEM 37 



63 



Problem 3G: To show that food is needed by the emhryu in 

 order to grow. 



Materials. — Growing pea and bean seedlings. 



Method. — We have ah-eady found that beans contain a supply 

 of food for the young plant. Test peas to see if food is also pres- 

 ent in the cotyledons. After the peas and beans have begun to 

 germinate remove the cotyledons and place them under favor- 

 able conditions for continued growth. What happens? Allow 

 bean seedlings to grow to a height of an inch, then remove both 

 cotyledons from some, one cotyledon from others, and leave others 

 with both cotyledons for controls. Which grow most rapidly? 



Conclusion. — What do you conclude from these results? 



rrohleni 37. Is any part of the air necessary for combustion ? 



(Demonstration. ) 



NOTE. — We have seen that seeds use up food in order to urow and that .-^ocds 

 grow only in the presence of air. We must now study the air in order Xm fintl wliat 

 there is in it that enables seeds to use food and release the energy' necessary for 

 growth. 



