Germination. 25 



water, resumes its active state, and the cells of a certain 

 part of the seeds begin to increase in size and to divide 1 ' 

 (15), causing the tiny shoot to burst through the seed- 

 case. Germination is completed when the young plant 

 (plantlet) is sufficiently developed to live without fur- 

 ther aid from the seed. 



29. Moisture is Essential to Germination. Air-dry 

 corn or other seeds will not germinate if kept however 

 long in a warm room, whereas viable seeds, that have 

 absorbed water until fully swollen, will usually germi- 

 nate if exposed to air of a suitable temperature, under 

 conditions that prevent their loss of moisture. This 

 shows that a certain amount of moisture must be ab- 

 sorbed by the seed before germination can take place. 

 Seeds must be nearly or quite saturated with water be- 

 fore they will germinate. 



In culture we plant seeds in some moist medium; 

 usually the soil, in order that they may absorb moisture 

 and germinate, and thus develop into new plants. 



30. Warmth is Essential to Germination. Had we 

 placed the seed-tester mentioned in paragraph 28 in a 

 refrigerator in which the temperature never rises above 

 41 F., instead of in a warm room, the corn grains 

 would not have germinated however long they remained 

 there. This shows that a certain degree of warmth is 

 also necessary to germination. Without this, the pro- 

 toplasm of the seed cannot assume its active state (13). 

 The lowest (minimum} temperature at which seeds can 

 germinate varies considerably with different species, 

 and so does the temperature at which they germinate 

 soonest (optimum} as also the highest (maximum} tern- 



