426 BOTANICAL GAZETTE [December 



Method 



The method consisted in stretching vertically a growing inter- 

 node, or parts of two adjacent internodes, and measuring the 

 amount of twist and the corresponding length. The object of this 

 stretching is, while giving support, to eliminate twining proper, 

 and the amount of stretching is slightly greater than that required 

 to accomplish this. An estimate of the torsional rigidity at differ- 

 ent lengths was also made. In certain experiments I have compared 

 this with the diameter and with the amount of lignification. I 

 have also begun studies on antidromous torsion, and have made a 

 few other observations. 



The apparatus is illustrated in figs. 1-4. There stands on a 

 base an upright {Up) about i m, high. This has a top piece bear- 

 ing two wheels {W and W) , over which runs a fine silk thread. On 

 the upright are also two sliding clamps {K and K'), which can be 

 secured at any height. The lower of these {K) has an arm bearing 

 a special kind of clamp {CI) for holding the lower part of the growing 

 internode. The other {K') carries a telescope {T) and a semi- 

 circular scale {Sc), which is graduated on the inside so as to read 

 half-degrees. I found 28 cm. a convenient diameter for this scale. 

 The upper part of the internode used is held by the frame {F), 

 which is suspended by the silk thread already mentioned. The 

 weight {Wt) supplies the proper amount of tension. By means 

 of the scale {Sc'), graduated so as to read o. i mm., and the double 

 pointer (/, //) on the wheel {W') the increase in length can be 

 obtained accurately, while this value can be obtained roughly by 

 means of a linear scale hung near the thread on this side of the 

 apparatus, but omitted from the figure for the sake of clearness. 

 There is a curved guard {G) to protect the pointers. 



The frame {F) requires more detailed description. It consists 

 of a bow of heavy wire, 2 . 2 mm. thick and about 1 2 cm. in diameter, 

 closed by a yoke {Yk) and suspended by a block of wood which 

 holds four mirrors {M). These mirrors (fig. 2), each one 1.2 cm. 

 in diameter (or better i.o cm.), are arranged in two pairs at right 

 angles, and are held together by means of a piece of sheet metal 

 (best of aluminum), which is cut to resemble roughly a cross and 

 then bent into the form shown. These mirrors are held in place 



