100 



PLANT BIOLOGY 



c. What parts of the oldest seedling have developed from 



the plumule? 



10. Draw the oldest stage of the bean seedling, and label 

 main or primary root, root-branches or secondary 

 roots, ground level, cotyledons (or scar left by coty- 

 ledons), hypocotyl, stem above cotyledons (epicotyl), 

 leaves, terminal bud. 



108. Study of the corn seedling and its development from 

 the corn grain. Laboratory Study No. 52. (Optional.) 



Materials: Dry and soaked corn grains; seedlings of various 

 sizes grown as described above for the bean seedling. Corn grains 

 should be planted with the pointed end down. 



The structure of the corn grain and the development of the com 

 embryo can be understood much more easily if the study of the 

 corn seedling is made first, and later that of the corn grain. 



A. Seedling just breaking ground. 



1. Examine a pot of seedlings that are just pushing their 



way through the soil or sawdust, and study a 

 seedling of this stage that is 

 given you. All the parts of 

 the seedling above the corn 

 grain have developed from 

 the first bud or plumule. 



a. What is the shape of the part that 



first breaks through the soil? 



b. Look for the sheath leaf sur- 



rounding the unfolding 

 leaves, and trace it down to 

 the ridge around the stem 

 from which it springs. How 

 does this sheath or first leaf 

 of the plumule differ from 

 the unfolding leaves? What 

 is its probable use? 



2. Observe the scar on the grain, showing where it was 



fastened to the cob, and notice the shape of the 



FIG. 46. Wheat Seedling. 



