204 



PROPAGATION BY SEEDS AND SPORES 



This has led to the practice of soaking seeds before sow- 

 ing, especially hard-coated ones like asparagus or canna 

 seed, to hasten germination. Beans and corn are some- 

 times soaked overnight before planting. 



Temperature. Few seeds will germinate in a tempera- 

 ture below freezing. It is because of low temperature that 

 weed seeds fail to grow during the winter, and remain dor- 

 mant until the soil becomes warmed by the sun in the 



spring. Corn fails to 

 germinate if planted too 

 early in the spring while 

 the soil is still cold. 

 The required temper- 

 ature, however, varies 

 with different seeds. The 

 seeds of peas, radishes, 

 and lettuce germinate 

 at a lower temperature 

 than corn and many 

 other garden seeds. For 



most seeds, a tempera- 

 Fig. 113. Sowing seeds. An even depth of , r o f o F - 

 seeds in fine, moist soil promotes good LUre OI y^ LO QO r . IS 

 germination. u ~ 



best. Great extremes 



between the temperature of the day and that of the night 

 retard germination. With small delicate seeds extremes 

 of temperature are exceedingly injurious. 



Oxygen. Free oxygen is essential for germination. 

 This element is required in the process by which the stored- 

 up food in the seed is made available for the young plant. 

 Seeds, if soaked in a jar of water, will enlarge and appar- 

 ently start to germinate, but if kept submerged and the 

 surface of the water oiled to prevent oxygen from reaching 



