Chap, IX.] SUMMARY OP THE CilAPTER. 183 



lead and two salts of barium were not poisonous to this 

 plant. It is an equally strange fact, that, though acetic and 

 propionic acids are highly poisonous, their ally, formic acid, 

 is not so; and that, whilst certain vegetable acids, namely, 

 oxalic, benzoic, &c., are poisonous in a high degree, gallic, 

 tannic, tartaric, and malic (all diluted to an equal degree) 

 are not so. Malic acid induces inflection, whilst the three 

 other just named vegetable acids have no such power. But a 

 pharmacopoeia woidd be requisite to describe the diversified 

 effects of various substances on Drosera.' 



Of the alkaloids and their salts which were tried, several 

 had not the least power of inducing inflection ; others, which 

 were certainly absorbed, as shown by the changed colour of 

 the glands, had but a very moderate power of this kind; 

 others, again, such as the acetate of quinine and digitaline, 

 caused strong inflection. 



The several substances mentioned in this chapter affect 

 the colour of the glands very differently. These often be- 

 come dark at first, and then very pale or white, as was con- 

 spicuously the case with glands subjected to the poison of the 

 cobra and citrate of strychnine. In other cases they are 

 from the first rendered white, as with leaves placed in hot 

 water and several acids ; and this, I presume, is the result of 

 the coagulation of the albumen. On the same leaf some 

 glands become white and others dark-coloured, as occurred 

 with leaves in a solution of the sulphate of quinine, and in 

 the vapour of alcohol. Prolonged immersion in nicotine, 

 curare, and even water, blackens the glands; and this, I be- 

 lieve, is due to the aggregation of the protoplasm within 

 their cells. Yet curare caused very little aggregation in the 

 cells of the tentacles, whereas nicotine and sulphate of qui- 

 nine induced strongly marked aggregation down their bases. 

 The aggregated masses in leaves which had been immersed 

 for 3 hrs. 15 m. in a saturated solution of sulphate of quinine 



Seeing that acetic, hydro- materially Influenced by any of 



cyanic, and chromic acids, ace- the poisons used, which did not 



tate of strychnine, and vapour of act chemically, with the exccn- 



ether, are poisonous to Drosera, tlon of chloroform and cnrbonlc 



It Is remarkable that Dr. Kansom acid." I find It stated by several 



(' Pbllosoph. Transact." 18<57, p. writers that curare has no Influ- 



480), who used much stronger ence on sareode or protoplasm, 



solutions of these substances and we have seen that, tbouKb 



than I did, states " that the curare excites some degree of In- 



rhytbmic contractility of the yolk flection. It causes very little ag- 



(of the ova of the pike) Is not gregatiou of the protoplasm. 



