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mip;lit go fuftliei- and state tliat, because tlie sense-perception is 

 wanting in tiie plants, their iiending miglit be compaied with the 

 purely retlectoiy movements of animals. 



However, although it must be admitted tiiat within the scope of 

 phj'siology comparisons between plants and animals may be success- 

 fully drawn in many cases (as is probable especially with regard 

 to stimulation, for the reason that in both groups of living organisms 

 one and the same relation appears to exist between stimulus-inten- 

 sity and stimulus-effect: the law of Wf.ber), this must be done 

 always with the greatest caution. Bearing this in mind it nevertheless 

 appears to me that the facts furnish us with sufiicient reason to 

 assume the striving on the part of the plant to receive the greatest 

 possible stimulation by the quickest way as a supposition, just 

 as we know this is the case with regard to positive chemotaxis. 

 It must be left to later researches to reduce this striving after 

 maximal stimulation to an actual cause of movement. 



With the aid of a number of examples taken from the different 

 groups of auxotonic movements, I now wish to demonsti'ate very 

 siiortly how simple the explanation of these phenomena becomes 

 when we set forth from the assumptions mentioned above. 



The different movements may be brought to certain groups according 

 to the (supposed) position of the static apparatus and to the shifting 

 which it should undergo. 



A. Stimulation by Gravitation. 

 1. Stationary position of the static apparatus. 



a. In the first place the static apparatus might lie against the 

 lowest transverse wall of the statocyst. This should be so in the 

 case of the vertically-growing main-root and main-axis, where the, 

 maximal, stimulus should be the cause of the vertical growth of 

 l>otli by the equal lengthening of the cells alliound. 



If these same organs be placed in another position, e. g. horizont- 

 ally, they will show positive (root) or negative (stem) geotropism. 

 This we should now try to explain by the striving after a stronger 

 stimulation. In the horizontal position the starch-grains press upon 

 a part of the less sensitive border of the .static apparatus; if they 

 have to come into contact with the middle-field, the most sensitive 

 part, the root will have to bend downwards, the stem, on the other 

 hand, upwards. The explanation of these opposite movements requires 

 therefore no new supposition ; it follows from the circumstance that 

 in the statocyst the middle-field in the case of the root lies against 

 the transverse wall which is turned away from the growing-zone 



