Malic Acid.—­Three leaves were immersed in ninety minims of a solution of one part to 437 of water; no inflection was caused in 8 hrs. 20 m., but after 24 hrs. two of them were considerably, and the third slightly, inflected—­more so than could be accounted for by the action of water.  No great amount of mucus was secreted.  They were then placed in water, and after two days partially re-expanded.  Hence this acid is not poisonous.

Oxalic Acid.—­Three leaves were immersed in ninety minims of a solution of 1 gr. to 437 of water; after 2 hrs. 10 m. there was much inflection; glands pale; the surrounding fluid of a dark pink colour; after 8 hrs. excessive inflection.  The leaves were then placed in water; after about 16 hrs. the tentacles were of a very dark red colour, like those of the leaves in acetic acid.  After 24 additional hours, the three leaves were dead and their glands colourless.

Benzoic Acid.—­Five leaves were immersed, each in thirty minims of a solution of 1 gr. to 437 of water.  This solution was so weak that it only just tasted acid, yet, as we shall see, was highly poisonous to Drosera.  After 52 m. the submarginal [page 195] tentacles were somewhat inflected, and all the glands very pale-coloured; the surrounding fluid was coloured pink.  On one occasion the fluid became pink in the course of only 12 m., and the glands as white as if the leaf had been dipped in boiling water.  After 4 hrs. much inflection; but none of the tentacles were closely inflected, owing, as I believe, to their having been paralysed before they had time to complete their movement.  An extraordinary quantity of mucus was secreted.  Some of the leaves were left in the solution; others, after an immersion of 6 hrs. 30 m., were placed in water.  Next morning both lots were quite dead; the leaves in the solution being flaccid, those in the water (now coloured yellow) of a pale brown tint, and their glands white.

Succinic Acid.—­Three leaves were immersed in ninety minims of a solution of 1 gr. to 437 of water; after 4 hrs. 15 m. considerable and after 23 hrs. great inflection; many of the glands pale; fluid coloured pink.  The leaves were then washed and placed in water; after two days there was some re-expansion, but many of the glands were still white.  This acid is not nearly so poisonous as oxalic or benzoic.

Uric Acid.—­Three leaves were immersed in 180 minims of a solution of 1 gr. to 875 of warm water, but all the acid was not dissolved; so that each received nearly 1/16 of a grain.  After 25 m. there was some slight inflection, but this never increased; after 9 hrs. the glands were not discoloured, nor was the solution coloured pink; nevertheless much mucus was secreted.  The leaves were then placed in water, and by next morning fully re-expanded.  I doubt whether this acid really causes inflection, for the slight movement which at first occurred may have been due to the presence of a trace of albuminous matter.  But it produces some effect, as shown by the secretion of so much mucus.