362 Growth-Periodicity of the Potato Tuber. 



auxanometer methods to root-stocks by uncovering the root-stock 

 attaching a silver thread, running it horizontally to the open side 

 of the box passing over a horizontal roller and upward and finally 

 adding the linen (or silken) thread which runs on the small -ir- 

 cumference of the first wheel. Or in this case one wheel alone 

 could doubtless be used. This study of underground stems, as in 

 the grass root-stock, the potato rhizome or any other underground 

 stem, would throw some light upon the tuber and its method of 

 growth. A comparison of underground organs should be made 

 along this line. 

 May 5, 1891. 



PRELIMINARY NOTES ON THE EPINASTY AND HYPONASTY OF 



RAPHAiNus COTYLEDONS. — E. P. Sheldon. 



In presenting this evening some of the phases of our present 

 knowledge regarding the various positions assumed by dorsiven- 

 tral organs during their period of growth and development, 1 

 think I can do little better than to give a short outline of the views 

 held by prominent botanists on this point, and follow somewhat 

 the course of development of such views as outlined by Sydney 

 H. Vines, in his article on Epinasty and Hyponasty.* 



First in importance are the views of De Vries.f 



Here we have the first recognition of the fact that the growth 

 of the two sides of a dorsiventral organ is not equal. There may 

 be some growth on both sides of such an organ, but when the 

 growth of the upper side preponderates over the growth of the 

 lower organ it is said to be in a state of epinasty. When the re- 

 verse is true it is said to be in a state of hyponasty. 



De Vries does not agree with FrankJ in regard to the cause 

 of the position of such members. 



Instead of explaining their position by peculiar forms of geo- 

 tropic and heliotropic irritability, he considers them as a resultant 

 of the various forms of epinasty, hyponasty, and negative or posi- 

 tive heliotropism or geotropism. The observation of Sachs§ on 



*AnnaIs of Botany. Aug., 1889. 

 tDe Vries : Arb. d. bot. Inst, in Wiirzburg, i, 1874. 

 $Frank : Die natiirliche wagerichte Richtung von Pflanzentheilen 

 Leipzig, 1870. 



SSachs: Arb. d. bot. Inst, in Wiirzburg, 11, 1879. 



