744 MINNESOTA BOTANICAL STUDIES. 



stimuli — geotropic and heliotropic — upon an organ simultane- 

 ously in no wise affects the sensibility of the organ to each of 

 these stimuli, in opposition to the theory of "Specific energy, 

 of Mtlller, but that the reaction of one or the other may be me- 

 chanically suppressed, but not physiologically altered. 



The results of Vines' (V) and Detmer's (II) investigations as 

 to the nature of epinasty and hyponasty are so widely diverg- 

 ent, though obtained from the same material, that it was 

 deemed advisable to repeat the detail of their experiments. To 

 this end seeds of Helianthus, Cucurbita, and Phaseolus were 

 germinated in a dark chamber, and subjected to various condi-' 

 tions. The cotyledons remained closely pressed together for a 

 period of three to five days, but at the end of this time they 

 began to separate, and about the eighth day exhibited a diverg- 

 ence of 120° to 135°. This experiment included a large num- 

 ber of individuals of each species, and great precautions were 

 taken that all possibility of error be excluded. The exposure 

 of the plants to light during the short time necessary for daily 

 examination, was quite insufficient to vitiate the results. The 

 results of this set of experiments verifies Vines' conclusions 

 that epinasty is not induced by light, but may occur in dark- 

 ness as well. The fact that the cotyledons did not move 

 through an arc of 90° and attain a horizontal position is due to 

 the fact that the plant was not in a phototonic condition. The 

 epinastic growth shown by the cotyledons was clearly inde- 

 pendent of light, and Detmer's photo-epinasty and hyponasty 

 as such do not exist. Detmer's conclusions are repeated in the 

 recent edition of his text book, and no reference is made to the 

 contradictory results reached by Vines. 



The remaining experiments, extending over a period of four- 

 teen months, were devoted to the study of geotropism, helio 

 tropism, and epinasty in dorsiventral members. The material 

 used included one or more species of Taraxacum, Helianthus, 

 Nicotiana, Arisaema, and Lactuca. 



In the manipulation of the growing specimens it was found 

 to be much more convenient if they were carefully removed 

 from the pots in which they were grown, and the roots, with 

 the adhering mass of earth wrapped in sphagnum moss. 

 When prepared in this manner space sufficient for the move- 

 ment of the leaves through, an arc of 150° was obtained. The 

 plants were allowed to recover from this transplantation before 

 used for experimental purposes. In all of the experiments 

 young, vigorously-growing specimens were used, and care was 



