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XLVI. THE FORCES DETERMINING THE 

 POSITION OF DORSIVENTRAL LEAVES. 



R. N. Day. 



The work described in the following paper was undertaken 

 for the, purpose of determination of the relative value of vari- 

 ous forces operative in the production of the positions of dorsi- 

 ventral leaves, and to what extent the inherited and spontane- 

 ous trophies of these organs might be altered by outward 

 conditions. 



A paper covering these points and embracing a review of the 

 literature bearing upon the subject was published by Vines in 

 1890 (V). Vines' conclusions as given by himself are as fol- 

 lows: 



"(1) Epinasty, and also hyponasty, are not induced, but are 

 spontaneous movements; (2) dorsiventral members, so far as 

 my experiments go, are not negatively geotropic, the move- 

 ments hitherto described as negative geotropism being due to 

 hyponasty, and altogether independent of gravitation. " 



As may be seen by reference to the results of my experiments, 

 they confirm Vines' view of the general nature of epinasty 

 and hyponasty, which is in direct opposition to that of Detmer. 

 In the consideration of the second point in the summary given 

 above, I am, of course, unable to comprehend exactly what is 

 meant by "movements hitherto ascribed to negative geotrop- 

 ism." It seems reasonable to suppose, however, that reference 

 is here made to the upward movements of leaves in darkness, 

 — a conclusion which is not in harmony with the results de- 

 scribed below. 



Since the appearance of Vines' paper, Czapek (I) has publish- 

 ed a most valuable contribution to our knowledge of the combin- 

 ed reactions of heliotropism and geotropism. The chief interest 

 of his researches lies in the conclusion that the action of two 



The work recorded in this paper was performed under the direction and by the 

 aid of Prof. D. T. MacDougal. 



