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sensitiveness to touch, attracted general attention. In 1848 Bri'icke's 

 memoir upon the sensitive plant appeared. It was a model for thorough- 

 ness, for ingenious methods, and lucid deduction. From this clear and 

 unequivocal starting point it was comparatively easy to pass to the less 

 obvious forms of irritability, and since then many kinds of reaction to 

 stimulation in plants have been brought to light and made the subjects 

 of investigation. 



But admitting that plants have sensibility, that is, are capable of re- 

 sponding to stimuli, is far from admitting that they have senses. Active 

 protoplasm is always sensitive to some form of stimulation. If a bit of 

 fresh striated muscle, from the leg of a frog for instance, be struck, or 

 pricked with a needle, or shocked with a current of electricity, it will re- 

 spond by contraction ; and so will the protoplasm in the cells of ati onion 

 or other plant. Contractility is a universal property of living matter, 

 although diflFerent cells of the vegetable and animal structure display it in 

 varying intensity. There is, however much disparity between contractility 

 and sensation. Whether this disparity is real, that is whether there is 

 actual discontinuity, or whether it is only seeming, being the expression 

 of extremes, is an important inquiry. 



If we approach the subject from the opposite direction, we shall have a 

 very different point of view. There is no way of securing a just conception 

 of the extent and relations of an object, as of a house or a tree, like view- 

 ing it from different sides. To consider the contraction of the muscles of 

 the arm when the hand has touched an uncomfortably hot surface, is to 

 study the physiology of the movement, but to consider the mental dis- 

 turbance produced by the perception of heat, is to take a very different 

 point of view and study its psychological relations. One is the objective 

 and the other the subjective method; both have advantages. But both 

 methods should lead to a unity of conception ; and this should be a more 

 complete conception, than either method could give pursued by itself; 

 just as viewing a house from the east side and from the west, is better 

 than viewing it from one side alone. So far as I am aware, no writer has 

 presented the psychological side (if the expression may be used) of the 

 movements of plants, although the foremost investigators, Darwin, Sachs 

 and Frank, make the presentation of their physiological studies attractive 

 by use of psychological expressions. Darwin, in his work on climbing 

 plants, describes the behavior of a plant, which failed to secure a hold 

 upon a tall stick placed at a certain distance, the free end of the twiner, 



