TORSION STUDIES IN TWINING PLANTS 



H. V. Hendricks 



(with six figures) 



Introduction 



This paper deals with a certain phase of the physiology of 

 twining plants. It is an account of some experiments upon the 

 scarlet runner or flowering bean {Phaseolus multiflorus) and the 

 black or corn bindweed {Tiniaria Convolvulus [L.] Webb and Moq.), 

 in which a modified form of auxanometer was used. To a limited 

 extent the hop (Humulus Lupulus L.) was studied also. 



The attention which twining plants have received from many 

 observers has resulted in considerable literature on the subject. 

 The main facts, however, have been well summarized by Vines^ and 

 by Pfeffer.^ A resume of these accounts seems unnecessary for 

 our present purpose, but it is convenient, as well as in accord with 

 the views of these workers, to consider the phenomenon as in- 

 volving the following as its most striking factors: (i) circumnuta- 

 tion of the growing tip; (2) winding of the stem about its support; 

 (3) torsion of the stem in the same direction as the winding (ho- 

 modromous); (4) torsion in the opposite direction (antidromous). 

 The relation of these factors to one another is not perfectly under- 

 stood, and I shall not enter into any discussion regarding it. This 

 paper deals only with torsion of the stem. 



Not having ready access to the literature, the aid of Mr. Peter J. 

 Klaphaak, of the University of Michigan, was secured in looking 

 up references, and I desire to express my appreciation of his services. 

 In as extensive a review as it was possible to make, no reference 

 was found to any method of approaching the problem similar to 

 the one here described. 



' Vines, S. H., Lectures on physiology of plants. 1886. 



2 Pfeffer, W., Physiology of plants, translated by A. J. Ewart, Vol. III. 

 1906. 



425] [Botanical Gazette, vol. 68 



