PHYSIOLOGICAL PROCESSES IN PLANTS 57 



2. Put some crushed cotyledon on a piece of paper, put it 

 in a hot place and leave it for several hours. What results? 



Conclusions. 1. What other food materials do you think 

 are present ? Reasons ? 



2. What foods then form most of the first food of the young 

 bean plant? 



3. Where is most of the nourishment for the growing bean 

 embryo stored? 



3. ANOTHER USE OF THE MICROPYLE (OPTIONAL) 



Method a. Observations. 1. Cover the micropyles of a few beans with 

 vaseline. Select as many more not covered with vaseline and weigh both 

 lots. Leave both lots in 

 water over night. Re- 

 weigh. What difference in 

 weight do you find ? What 

 difference in appearance, 

 if any ? 



Conclusions. 1. What 

 is one of the uses of the 

 micropyle ? 



2. What other use of the 

 micropyle do you already 

 know? 



Method b. Observations. 1. Fill a cigar box with wet sand or sawdust. 

 Place on the surface some corn grains or beans in rows, one third with the 

 micropyle up, one third with the opening down, and one third flat on the 

 soil as in Figure 10. Press them firmly into the soil so that each is just 

 half buried. Which sprout first ? 



Conclusions. 1. Where may the water enter seeds ? 



2. Does the seed's natural position in the soil usually bring the opening 

 in contact with the earth ? Explain. 



b. How the Young Plant Makes Use of the Food Supply 

 1. DIGESTION 



Observations. 1. Cut lengthwise through the embryo of a 

 number of corn grains that have just begun to germinate. Place 

 them in a test tube and test for grape sugar. (Look for 



FIG. 10. Seeds half submerged in wet sand or 

 sawdust, to determine how the water enters. 

 (After Osterhout.) 



