Boracic Acid.—One to 437 of water; four leaves were immersed together in 120 minims; after 6 hrs. very slight inflection; after 8 hrs. 15 m. two were considerably inflected, the other two slightly. After 24 hrs. one leaf was rather closely inflected, the second less closely, the third and fourth moderately. The leaves were washed and put into water; after 24 hrs. they were almost fully re-expanded and looked healthy. This acid agrees closely with hydrochloric acid of the same strength in its power of causing inflection, and in not being poisonous. Formic Acid.—Four leaves were immersed together in 120 minims of one part to 437 of water; after 40 m. slight, and after 6 hrs. 30 m. very moderate inflection; after 22 hrs. only a little more inflection than often occurs in water. Two of the leaves were then washed and placed in a solution (1 gr. to 20 oz.) of phosphate of ammonia; after 24 hrs. they were considerably inflected, with the contents of their cells aggregated, showing that the phosphate had acted, though not to the full and ordinary degree. Acetic Acid.—Four leaves were immersed together in 120 minims of one part to 437 of water. In 1 hr. 20 m. the tentacles of all four and the blades of two were greatly inflected. After 8 hrs. the leaves had become flaccid, but still remained closely inflected, the surrounding fluid being coloured pink. They were then washed and placed in water; next morning they were still inflected and of a very dark red colour, but with their glands colourless. After another day they were dingy-coloured, and [page 192] evidently dead. This acid is far more powerful than formic, and is highly poisonous. Half-minim drops of a stronger mixture (viz. one part by measure to 320 of water) were placed on the discs of five leaves; none of the exterior tentacles, only those on the borders of the disc which actually absorbed the acid, became inflected. Probably the dose was too strong and paralysed the leaves, for drops of a weaker mixture caused much inflection; nevertheless the leaves all died after two days.