THE SEED, GERMINATION AND THE PLANTLET 17 



capable of germination. In seeds in this condition, the 

 seed-case will be burst by the pressure of a tiny white 

 shoot from beneath. We say that such grains have 

 sprouted or begun to germinate, i.e., have taken the first 

 visible step toward developing into an independent plant. 

 We have seen that the mature seed contains protoplasm 

 in a dormant condition (13). At a suitable temperature, 

 the protoplasm, on the absorption of water, resumes its 

 active state, and certain cells begin to increase in size 

 and to divide (15), causing the tiny shoot to burst through 

 the seed-case. Germination is completed when the young 

 plant (plantlet) is sufiiciently developed to live without 

 further aid from the seed. 



29. Moisture 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 germinate 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 absorbed by the seed before 

 germination can take place. Seeds must be nearly or 

 quite saturated with water before 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 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 ger- 

 minated however long they remained there. This shows 

 that a certain degree of warmth is also necessary to ger- 

 mination. Without this, the protoplasm of the seed 

 cannot resmne its active state (13). The lowest (mini- 



