SEEDS AND SEEDLINGS 



123 



(i.e. J the most favorable temperature) ranging from about 75 

 to 100 degrees Fahronlieit for our garden, and farm crop seeds. 

 If the temperature is not the most favorable the rate of germina- 

 tion will be decreased. 



Oxygen is also necessary for the germination of seeds. The 

 oxygen is obtained from the air and therefore it is necessary to 

 have the soil loose and the seeds planted at the proper dep'th. 



Processes of Germination. — The processes of germination 



Fia. 87.— (a) Longitudinal section of corn seed showing the embryo; (6) and (c) the 

 germinating seed showing the emergence of the root and plumule, the formation of root- 

 lets and root-hair. 



are both physical and chemical. Very briefly, they are the ab- 

 sorption of water, the digestion of the stored foods and the trans- 

 portation of the same to such parts as may be necessary for 

 growth. The digestion of the food is brought about by special- 

 ized substances, known as enzymes, which are also stored in the 

 seeds. The processes of digestion and translocation will receive 

 further discussion in Chapter XVIII. 



