TREES INVENTED AIRPLANES 
selves all about river bottoms, nestle in the grass, catch in 
the drifts, and get buried in the sand. 
The idea of the mother tree in putting wings on her 
seeds is that they may escape the shade that she herself 
makes and find less crowded conditions far away. Wise 
as this device is, it results in sending nearly all these 
tree children away on quite fruitless journeys. For one 
tree seed that lives and grows to lift its crest to the sky, 
millions perish. 
The willow or cottonwood tree, for example, gives mil¬ 
lions of seeds to the winds every year. If one per cent of 
these seeds grew to be trees, they would overrun the 
world. The death rate is high among tree babies. Na¬ 
ture is anything but economical when she sets about 
planting her crops. 
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