62 PHYSIOLOGICAL PROCESSES IN PLANTS 



Method. Plant the soaked seeds in pots or shallow trays, 

 with holes in the bottom for drainage. Plant them in moist 

 sand or sawdust. Use a box with glass side for studying root 

 development. Keep the temperature about 72 F., and water 

 them occasionally. Take out specimens from day to day until a 

 complete series is obtained up to the time green leaves appear. 



Make sketches of these changes every other day, for about 

 two weeks. The series of .sketches should show just what has 

 become of each part of the embryo. 



a. The Bean Seedling 



Note. A growing plant is called a seedling until it loses its 

 seed leaves, or cotyledons. 



Observations. 1. Which part of the embryo breaks through 

 the seed coats first ? Where ? 



2. Into what does the hypocotyl develop ? 



3. What part appears first above ground ? 



4. Are the cotyledons of the bean pushed or pulled out of 

 the ground ? 



5. What change takes place in the size of the cotyledons ? 

 Color? 



6. What becomes of the cotyledons in old specimens ? 



7. What color has the part above ground ? 



Conclusion. What does the change in size of the cotyledons 

 indicate ? 



Drawing. Draw a horizontal line across a sheet to represent the level 

 of the sawdust or other material used. On this line make a series of 5 

 sketches, showing just what has become of the cotyledons, hypocotyl, 

 and plumule. Label these parts. 



b. Pea Seedling (Optional) 



Observations. 1. Can you find the same external structures in the 

 pea as were found in the bean ? Name them. 



2. Remove the seed coat from a soaked seed. How many cotyledons 

 do you find ? 



Note. Plants whose seeds contain two cotyledons are said to be 

 dicotyledons. 



