PLANT GROWTH AND NUTRITION 



63 



Germination of the Bean. — If dry seeds are planted in sawdust 

 or earth, they will not grow. A moderate supply of water must be 



A series of early stages in the germination of the kidney bean. 



given to them. If seeds were to be kept in a freezing tempera- 

 ture or at a very high temperature, no growth would take place. 

 A moderate temperature and 

 a moderate water supply are 

 most favorable for their de- 

 velopment. 



If some beans were planted 

 so that we might make a record 

 of their growth, we would find 

 the first signs of germination 

 to be the breaking of the testa 

 and the pushing outward of 

 the hypocotyl to form the first 

 root. A little later the hypo- 

 cotyl begins to curve down- 

 ward. A later stage shows 

 the hypocotyl lifting the coty- 

 ledon upward. In consequence 

 the hypocotyl forms an arch, 

 dragging after it the bulky 



. 1 ^ mi J. Bean seedlings. The older seedlings at 



cotyledons. The stem, as ^^^ ^^^^ ^^^^ ^sed up all of the food 

 soon as it is released from the supply in the cotyledons. 



