PLANT INTELLIGENCE 
tering into intellectual states of pleasure or 
pain. 
In view of what has already been said, it 
hardly seems necessary to prove the existence of 
sensation in plants. The very fact that all life 
is a constant response to stimuli and the adjust- 
ment to environment presupposes the existence 
of plant sensation. Only a few hours passed in 
the investigation of plant habits will show our 
vegetable friends giving definite responses to 
heat, cold, moisture, light, and touch, while 
laboratory experiments show their sensitive 
powers of taste and hearing. 
The touch sense of the Sundew is developed 
to such an extent that it can detect the pressure 
of a human hair one twenty-fifth of an inch 
long. The tendrils of the Passion Flower at- 
tempt to coil up at the slightest contact of the 
finger and as quickly flatten out upon its re- 
moval. The stamens of the Opuntia or Prickly 
Pear have specialized papillae of touch ex- 
actly similar to the papillae of the Hermione 
Worm. When rubbed by the body of an in- 
sect, they transmit an impulse which causes 
the anthers to let loose a shower of pollen on 
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