CHAP. II SEEDLINGS 13 



VI. Examine several pots containing seedlings of the 

 Castor Bean of various ages. Notice that : 



1. The caulicle first breaks through the surface of the soil 



and is bent into a " loop," both ends being still 

 buried. 



2. The " loop " increases in size and rises higher and higher 



until 



3. At length the main body of the seed begins to break 



through the surface of the ground. 



4. The outer seed-coat {testa) is usually left behind in the 



ground, but the inner seed-coat (tegmeii) with the 

 enclosed endosperm and cotyledons is pulled out of 

 the ground by this action of the caulicle. 



5. Older seedlings will show how the cotyledons gradually 



separate from one another while still absorbing nour- 

 ishment from the endosperm, but 



6. They finally separate widely along their whole .length, 



throwing off the tegmen and what is left of the endo- 

 sperm, and are ready to do the work of leaves, as is 

 shown by their expanding and turning green. 



7. Make a series of sketches to illustrate these points. 



8. Compare the cotyledons with one of the leaves of an 



adult plant of the Castor Bean as regards size, shape, 

 color (of both surfaces), and venation (arrangement 

 of the veins or ribs) . 



VII. Take a pot of fairly well grown seedlings of Indian 

 Corn and notice that : 



i. 



The plumule, enwrapped in the tip of the cotyledon, 

 is the first part of the seed to appear above the 

 ground. 



