52 MOVEMENTS OF PLANTS 



chain of thoughts or actions each caUing forth the 

 next. 



What I wish to insist on is, that the process I 

 have called action-by-signal is of the same type as 

 action-by-association, and therefore allied to habit 

 and memory. The plants alive to-day are the 

 successful ones who have inherited from successful 

 ancestors the power of curving in certain ways, 

 when, by accidental deviations from their normal 

 attitude, some change of pressure is produced in 

 their protoplasm. With the pianist the playing of 

 A has become tied to, entangled or associated with, 

 the playing of B, so that the striking of note A 

 has grown to be a signal to the muscles to strike 

 B. Similarly in the plant, the act of bending has 

 become tied to, entangled or associated with, that 

 change in the protoplasm due to the altered posi- 

 tion. There is no mechanical necessity that B 

 should follow A in the tune ; the sequence is owing 

 to the path built by habit in the man's brain. And 

 this is equally true of the plant, in which an here- 

 ditary habit has been built up in a brain-like root- 

 tip. 



The capacities of plants of which I have spoken 

 have been compared to instincts, and if I prefer to 

 call them reflexes it is because instinct is generally 

 applied to actions with something of an undoubted 

 mental basis. I do not necessarily wish it to be 

 inferred that there can be nothing in plants which 

 may possibly be construed as the germ of conscious- 

 ness — nothing psychic, to use a convenient term ; 

 but it is clearly our duty to explain the facts, if 

 possible, without assuming a psychological resemb- 



