which had caught a small insect, one such mass was observed to undergo
incessant changes of form, with the occasional appearance of vacuoles.
But I do not believe that this protoplasm had been generated by matter
absorbed from the dead insect; for, on comparing several glands which
had and had not caught insects, not a shade of difference could be
perceived between them, and they all contained fine granular matter. A
piece of leaf was immersed for 24 hrs. in a solution of one part of
carbonate of ammonia to 218 of water, but the hairs seemed very little
affected by it, excepting that perhaps the glands were rendered rather
more opaque. In the leaf itself, however, the grains of chlorophyll
near the cut surfaces had run together, or become aggregated. Nor were
the glands on another leaf, after an immersion for 24 hrs. in an
infusion of raw meat, in the least affected; but the protoplasm lining
the cells of the pedicels had shrunk greatly from the walls. This
latter effect may have been due to exosmose, as the infusion was
strong. We may, therefore, conclude that the glands of this plant
either have no power of absorption or that the protoplasm which they
contain is not acted on by a solution of carbonate of ammonia (and this
seems scarcely credible) or by an infusion of meat.
Nicotiana tabacum. This plant is covered with innumerable hairs of
unequal lengths, which catch many minute insects. The pedicels of the
hairs are divided by transverse partitions, and the secreting glands
are formed of many cells, containing greenish matter with little
globules of some substance. Leaves were left in an infusion of raw meat
and in water for 26 hrs., but presented no difference. Some of these
same leaves were then left for above 2 hrs. in a solution of carbonate
of ammonia, but no effect was produced. I regret that other experiments
were not tried with more care, as M. Schloesing [page 353] has shown*
that tobacco plants supplied with the vapour of carbonate of ammonia
yield on analysis a greater amount of nitrogen than other plants not
thus treated; and, from what we have seen, it is probable that some of
the vapour may be absorbed by the glandular hairs.]
A Summary of the Observations on Glandular Hairs. From the foregoing
observations, few as they are, we see that the glands of two species of
Saxifraga, of a Primula and Pelargonium, have the power of rapid
absorption; whereas the glands of an Erica, Mirabilis, and Nicotiana,
either have no such power, or the contents of the cells are not
affected by the fluids employed, namely a solution of carbonate of
304