Seeds and Their Germination. 



23 



different from those that appear later? Which of these 

 three plants shows the real nature of cotyledons ? 



Have your buckwheat embryos yet shown you what 

 they do with the endosperm? Why do they hold on to 

 their coats after they come up ? 



Draw several of the buckwheat seedlings. 



EXERCISE 16. 



Compare the roots of your seedlings. Do you find hairs 

 on any of them ? Where do the hairs grow ? If, in your 

 experiments with beans in the jar, you failed to determine 

 how roots grow, try marking with India-ink the central root 

 of a sunflower after the side roots have begun to grow. 

 Place dots the whole length at intervals of about one-tenth 

 of an inch. Cut thin cross-sections of the 

 hypocotyl and the central root of the 

 largest seedling sunflower. Can you with 

 the help of a lens see any difference in 

 their structure ? What do you think can 

 enter the roots ? Can particles of earth 

 be taken in by them? What do you 

 think are the uses of roots to the plants ? 



EXERCISE 17. 



When your castor-beans come up com- 

 pare their appearance with the drawing 

 on this page. 



Why do the cotyledons remain so long 



Fig. 17. Germinating 

 castor-bean, showing 

 the hard coat yet adher- 

 ing to the inner much- 

 enlarged coat, which 

 forms a sack holding 

 the growing cotyledons 

 and the endosperm, 

 which they are ab- 

 sorbing. 



