Tendrils of Cucurbitacece. 245 



forms of balances were used. Of these, the first was a tor- 

 sion balance formed of a brass spring 9.5 cm. long and 1.6 

 cm. diameter, bearing upon the free end a grooved wheel 

 6.5 cm. in diameter. This operated against an arbitrarily 

 graduated scale, and carried an index hand. Over the 

 wheel there passed a light, flexible wire, which was drawn 

 through a metal eye fastened to the scale plate, and pro- 

 vided with a suitable loop at the end for the tendril to 

 grasp. The balance was adjusted to an initial tension of 

 5.31 gr., and a total tension of 254.93 gr. The second 

 balance was constructed of a clock spring with post adjust- 

 ment, so that the tension could be varied at pleasure. The 

 spring operated upon the face of a board, and from the free 

 end of the former a light wire was led through metal eyes 

 along a horizontal scale, and provided with a suitable loop 

 at the end. The adjustment was made for an initial tension 

 of 120 gr., and a total tension of 900 gr. In both of these 

 instruments the divisions were arbitrary, their value in 

 grains being determined experimentally. The latter was 

 not used at all, and the former to but a limited extent, for 

 reasons soon to appear. 



The third and most simple form of instrument, and that 

 which was chiefly relied upon, consisted of a square stick 

 about 30 cm. long, upon which was fixed a scale in centi- 

 metres. Into the end of the stick was firmly fixed a small 

 hook, upon which could be hung the brass spring for direct 

 tension. In this apparatus three springs in all were used, 

 though the two first to be mentioned were employed in 

 nearly all the determinations. Their dimensions were as 

 follows : — 



Length. Diam. of Spring. Diam. of Wire. 



1 - - - - 9.7 cm. 0.3 cm. 0.25 m.m. 



2 - - - - 11.7 " 0.6 " 0.50 " 



3 - - - - 19.5 " 1.0 " 1.00 " 



In using these balances, the spring was hung upon the 

 hook and allowed to run along the scale. To it, the free end 

 of the tendril was then secured by suitable means, and the 

 strain exerted by a direct and steady pull. Readings were 

 then taken of the elongation of the spring, and the value in 



