Dormancy and Germination of Seeds 271 



soil should be at least as high as this when seeds are planted. 

 If the temperature is much lower, the vitahty of the seedling is 

 reduced, and the plant is then more readily attacked and injured 

 or destroyed by bacteria and fungi. On the other hand, when 

 germination occurs in soil that is higher than 70° F., many plants 

 form very poor root systems ; consequently the growth of the 

 plant is retarded. 



The germination of most seeds takes place equally well in light 

 or in darkness. Light retards the germination of some seeds, 

 while others, like those of bluegrass, certain varieties of tobacco, 

 mullein, and mistletoe, germinate better in the light. 



Seedlings. Recent experiments have definitely proved that 

 large, vigorous plants develop only from vigorous seedlings. In 

 many plants large seeds produce better seedlings than small 

 seeds. Therefore, in order to produce the best plants we must 

 start with seeds of good quahty and we must make sure that the 

 seedlings are not interfered with during their early development. 

 Planting many seeds in a row and then removing all but the most 

 vigorous of the seedlings is, therefore, good agricultural practice. 

 Removing weeds and keeping the soil porous and fairly moist 

 keep up the water and oxygen supphes for the roots and prevent 

 any interference with the hght that the seedlings should receive 

 for food manufacture. 



