LIFE HISTORIES OF FAMILIAR PLANTS 



equally plain. Naturally, a seed winged only on 

 one side, or with nearly all its weight in one 

 direction, owing to its centre of gravity having 

 an eccentric position, would spin in falling ; hence, 

 as the seed has developed and broadened its 

 wings, this gyratory movement has continued, and 

 probably been strengthened from the fact, which 

 I have previously pointed out, that it helps the 

 seed to penetrate the earth when its flight is sud- 

 denly interrupted. 



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