SENSITIVE PLANTS 



So the sensitive plant developed its talent 

 accOx^dingly, and to-day we marvel at its cunning 

 when it surprises and tricks the grazing animals 

 and others of its enemies ; but we must not over- 

 look the fact that there is in reality no such subtle 

 discrimination and cunning in its manoeuvres. 

 The plant acts exactly the same if a spot of water 

 is dropped upon its leaves as it would if a brows- 

 ing animal touched them with its nose, or as when 

 I blew at it before taking the photographs ; indeed, 

 the plant is quite unable to distinguish between 

 these external influences. But, by the mere fact of 

 these sensitive movements having served so good a 

 purpose in its economy, they became hereditary, 

 and were further evolved until the disturbance of 

 the atmosphere caused by oiu* approach, or by the 

 movement of our umbrella, or by the change of 

 light caused by our shadow being suddenly cast 

 across their leaves, was sufficient to influence 

 them ; just as, in a larger degree, would the 

 stronger wind and the greater darkness of an ap- 

 proaching storm influence them. 



Sensibihty in plants, however, does not begin, 

 or end, in the leaf structures. It exists in the 

 germinating seeds, and in every stage of their sub- 

 sequent development. From the seed emerges a 

 tiny root which penetrates the soil, but not as a 

 piece of stick might do. The root-tip quite fastidi- 

 ously selects its path amongst the interstices of the 

 soil, seeking out moist places and avoiding such 

 obstacles as will not provide suitable mineral food. 



If you examine the tip of a young root by 



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