98 



PLANT BIOLOGY 



4. Pinch a soaked seed, and notice the opening near the 



hilum through which water is forced from the 

 seed. This opening is called the micropyle (Greek, 

 micro = tiny + pula = gateway). 



a. Describe the position and appearance of the micro- 



pyle. What is the derivation of the word ? 



b. Sketch the micropyle in your drawing in 3 above. 



5. Carefully remove the seed-coat from a soaked bean. 



All the structures within this seed-coat together 

 . form a little bean plant, called a bean embryo. 

 Break off one of the two halves and make out the 

 following parts of thfe bean embryo: 1) the two 

 thickened halves of the bean called the seed leaves 

 or cotyledons; 2) a little sprout, the first stem or 

 hypocotyl (Greek, hypo = beneath + cotyl = cotyle- 

 don) ; and 3) the two tiny folded leaves forming 

 the first bud or plumule, lying between the cotyle- 

 dons. 



a. State what you have done to show the parts of the 



embryo. 



b. Name and describe each of these parts. 



c. Place the cotyledon you have removed close to its 



point of attachment to 

 the hypocotyl, and 

 make a drawing about 

 two inches long, show- 

 ing all the parts named 

 above, labeling each 

 part. 



6. Examine a bean seed that 

 has just begun to 

 sprout. 



a. Name the part of the 



bean embryo that first 

 breaks through the 

 seed-coats. 



b. Make a drawing about 



two inches long, to 



FIG. 44. Germination of castor show the Sprouted 



bean. (Osterhout.) Seed. Label. 



