PHYSIOLOGICAL PROCESSES IN PLANTS 



63 



3. Find the hypocotyl and plumule. Are they located in the same place 

 as in the bean ? 



4. Watch pea seedlings develop as with the beans. Which part comes 

 above ground first ? 



5. What parts of the seedling remain be-low ground ? 



6. What becomes of the cotyledons ? 



Conclusions. 1 . How do the cotyledons of the pea differ in use from 

 those of the bean ? 



2. What is the principal difference between bean seedlings and pea 

 seedlings ? 



Drawings. Make a series of sketches as with the bean seedling, 

 showing the different stages of germination and just what becomes of each 

 part of the embryo. Fill in the following table : 



c. Uses of the Cotyledons 



Method. Plant a few beans and peas in sawdust. After the 

 cotyledons or leaves have appeared above the ground remove 

 the cotyledons from half of each sort of seedling. Care for 

 the seedlings and examine from time to time for ten days or 

 so. What results? 



Conclusion. What is at least one use of the cotyledons 

 of the bean plant ? Of the pea ? 



d. The Corn Seedling (Optional) 



Observations. 1. Use soaked corn grains. Find a light-colored area 

 on one side. This marks the position of the embryo. Is it large or small 

 compared with the entire seed ? 



2. Cut a grain lengthwise through the narrow side, and find the embryo. 

 Verify your opinion in the preceding topic as to the comparative size of 

 the embryo. 



3. Put some iodine solution on the cut surface. Kesults ? 



Note. The embryo does not stain so deeply with iodine as the endo- 

 sperm. Endosperm is food material outside the embryo. 



