THE PROCESS OF GERMINATION 



173 



310. The young roots are not able to 

 gain a foothold. 



into soluble products. They are digested, so to speak, and 

 made available for assimilation by the protoplasm. Germi- 

 nate barley. Note how sweet 

 it is to the taste. Compare it 

 with the ungerminated barley. 

 Do likewise with corn and 

 wheat. What is the source of 

 the sugar? The seed-coats are 

 ruptured, the caulicle and 

 plumule emerge. In this pro- 

 cess, the seed respires freely, 

 giving off carbon dioxid (CO 2 ). 

 Fill a tin box or large-necked 

 bottle with dry beans or peas, then add water; note how 

 much they swell. Secure two fruit-jars. Fill one of them 

 a third full of beans and keep them 

 moist. Allow the other to remain empty. 

 In a day or two insert a lighted splinter 

 or taper into each. In the empty jar 

 the taper burns: it contains oxygen. 

 In the seed- jar the taper goes out: the 

 air has been replaced by carbon 

 dioxid. Usually there is a percepti- 

 ble rise in temperature in a mass 

 of germinating seeds. 



338. The caulicle usually elon- 

 gates, and from its lower end roots 

 are produced. The elongating 

 caulicle is known as the hypocotyl 

 ("below the cotyledons"). That 

 is, the hypocotyl is that part of the 

 stem of the plantlet lying between 

 the roots and the cotyledon. The 

 general direction of the young hypocotyl or emerging 

 caulicle is downwards. As soon as roots form, it becomes 



311. Cotyledons of germi- 

 nating bean spread apart 

 to show elongating cauli- 

 cle and plumule. 



312. Germination of bean. 



