38 



négative 105 min. 95 ? min. 



positive 140 „ 120—150 „ 



The agreement between observed values and the calcu- 

 lated ones is as striking as could be expected. 



The supposition that we hâve nutations hère, explains 

 fully the above mentioned six points, and I cannot see 

 how point 6 could be susceptible ofany other explanation. 

 Two questions only remain unanswered : first, why thèse 

 curvations in opposite direction hâve been seen in some 

 experiments only and further, why nearly ail the seedlings 

 were nutating in the same direction. 



With regard to the first point I look for an explanation 

 in the fact that thèse curvations became obvions as soon 

 as the atmosphère in the dark room became purer; this 

 quite agrées with our knowledge concerning nutations. ') 

 The circumstance, that I observed them, but rarely finds 

 an explanation in the fact, that this phenomenon can 

 appear only when stimulation lasts for a period slightly 

 longer than the presentation-time ; moreover I hâve excluded 

 thèse phenomena on purpose in séries C. as I hâve stimu- 

 lated in a direction perpendicular to the main direction 

 of nutation. 



The second question I cannot answer. The nutation at 

 the same moment and in the same direction of a set of 

 plants grown together — a fact mentioned by Rothert ") 

 too — points to the conclusion that nutations are not so 

 perfectly autonomous as they are generally believed to be. 

 The geotropic curvation thus présents itself at first as an 

 increased nutation of definite direction, in agreement 

 therefore with the views of Darwin ^), who reckons the 



1) 0. Rie h ter, 1909, p. 488. 



2) W. Rothert, 189i, p. 32. 



3) Cb. aud F. Darwin, 1880. 



