254 FRANCIS DARWIN. 



server or with an aspirator. Observations made in this way 

 established the fact that the vapour of chloroform causes con- 

 traction of the filaments. I recorded in one case that the 

 filament under observation "did not contract directly I tasted 

 the chloroform." The following observations show that chloro- 

 form produces a temporary narcosis of the filaments : — August 

 9th, 4.30 p.m. A filament was made to contract by the vapour 

 of chloroform ; by next morning at 9 a.m. it had altered in 

 shape, being more elongated than when it first contracted, al- 

 though it had by no means recovered its original whip-like 

 form. On drawing chloroform through the chamber it con- 

 tracted again. During this aspiration, a fully extended filament 

 was seen to contract;^ this filament had escaped the effect of 

 the previous da)''s chloroform, as it had not then been protruded. 

 Pure air was then rapidly drawn through the chamber, and by 

 one o'clock the second contracted filament had partially assumed 

 an elongated form, and was again made to contract by aspiring 

 the chloroform.^ 



Glycerine. — A preparation was irrigated with glycerine, and a 

 filament was seen to contract slowly, a sluggish- looking beading 

 making its appearance. It ultimately became spherical, and re- 

 mained unaltered for half an hour; it was then thoroughly 

 irrigated with water, and still continued unchanged in appearance. 



Syrup of sugar also produces contraction. 



Quinine. — An aqueous solution of -j-^ % of sulphate of 

 quinine was employed, and contraction was observed in several 

 cases. This result agrees with my father's observation . that 

 quinine is poisonous to Drosera.^ 



Camphor. — This substance was tried because my father has 

 shown it to be a powerful stimulant to Drosera.* The washing 

 bottle connected with the gas-chamber was half filled with water, 

 in which a few lumps of camphor were floating ; an atmosphere 

 strongly impregnated with camphor was thus produced. The 

 filament could not be made to contract by drawing the camphor- 

 laden air through the chamber. A V^ % {i.e. natural) solution 

 of camphor was prepared, and by irrigating with this fluid con- 

 traction was distinctly and repeatedly produced. Conwentz has 

 shown that camphor is a poison to the cells of Cladojahera fracia' . 



^ Contraction was here preceded bv an unusual appearance which may 

 be best described as a wrinkling, and is different from the niouiliform 

 contraction. 



' Tliere is nothinj^ very special in the narcotizing influence of cliloroform, 

 for filaments half killed by dilute acids have occasionally been observed in 

 a sluggish, narcotized state. 



' ' Insectivorous Plants,' p. 201. 



* Ibid., p. 209. 



* 'Bot. Zeitung,' 1874, pp. 401, 417. Goppert seems first to have 

 observed the poisonous cfl'ect of camphor on plants. 



