I made also several experiments on the action of the vapour of the carbonate on the glands; but will give only a few cases.  The cut end of the footstalk of a young leaf was protected with sealing-wax, and was then placed under a small bell-glass, with a large pinch of the carbonate.  After 10 m. the glands showed a considerable degree of aggregation, and the protoplasm lining the cells of the pedicels was a little separated from the walls.  Another leaf was left for 50 m. with the same result, excepting that the hairs became throughout their whole length of a brownish colour.  In a third leaf, which was exposed for 1 hr. 50 m., there was much aggregated matter in the glands; and some of the masses showed signs of breaking up into brown granular matter.  This leaf was again placed in the vapour, so that it was exposed altogether for 5 hrs. 30 m.; and now, though I examined a large number of glands, aggregated masses were found in only two or three; in all the others, the masses, which before had been globular, were converted into brown, opaque, granular matter.  We thus see that exposure to the vapour for a considerable time produces the same effects as long immersion in a strong solution.  In both cases there could hardly be a doubt that the salt had been absorbed chiefly or exclusively by the glands.

On another occasion bits of damp fibrin, drops of a weak infusion of raw meat and of water, were left for 24 hrs. on some leaves; the hairs were then examined, but to my surprise differed in no respect from others which had not been touched by these fluids.  Most of the cells, however, included hyaline, motionless little spheres, which did not seem to consist of protoplasm, but, I suppose, of some balsam or essential oil.

Pelargonium zonale (var. edged with white).—­The leaves [page 351] are clothed with numerous multicellular hairs; some simply pointed; others bearing glandular heads, and differing much in length.  The glands on a piece of leaf were examined and found to contain only limpid fluid; most of the water was removed from beneath the covering glass, and a minute drop of one part of carbonate of ammonia to 146 of water was added; so that an extremely small dose was given.  After an interval of only 3 m. there were signs of aggregation within the glands of the shorter hairs; and after 5 m. many small globules of a pale brown tint appeared in all of them; similar globules, but larger, being found in the large glands of the longer hairs.  After the specimen had been left for 1 hr. in the solution, many of the smaller globules had changed their positions; and two or three vacuoles or small spheres (for I know not which they were) of a rather darker tint appeared within some of the larger globules.  Little globules could now be seen in some of the uppermost cells of the pedicels, and the protoplasmic lining was slightly separated from the walls of the lower cells.  After 2 hrs. 30 m. from the time of first immersion, the large globules within the glands of the longer hairs were converted into masses of darker brown granular matter.  Hence from what we have seen with Primula sinensis, there can be little doubt that these masses originally consisted of living protoplasm.