Erica tetralix.—A few long glandular hairs project from the margins of
the upper surfaces of the leaves. The pedicels are formed of several
rows of cells, and support rather large globular heads, secreting
viscid matter, by which minute insects are occasionally, though rarely,
caught. Some leaves were left for 23 hrs. in a weak infusion of raw
meat and in water, and the hairs were then compared, but they differed
very little or not at all. In both cases the contents of the cells
seemed rather more granular than they were before; but the granules did
not exhibit any movement. Other leaves were left for 23 hrs. in a
solution of one part of carbonate of ammonia to 218 of water, and here
again the granular matter appeared to have increased [page 352] in
amount; but one such mass retained exactly the same form as before
after an interval of 5 hrs., so that it could hardly have consisted of
living protoplasm. These glands seem to have very little or no power of
absorption, certainly much less than those of the foregoing plants.
Mirabilis longiflora.—The stems and both surfaces of the leaves bear
viscid hairs. young plants, from 12 to 18 inches in height in my
greenhouse, caught so many minute Diptera, Coleoptera, and larvæ, that
they were quite dusted with them. The hairs are short, of unequal
lengths, formed of a single row of cells, surmounted by an enlarged
cell which secretes viscid matter. These terminal cells or glands
contain granules and often globules of granular matter. Within a gland
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.
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Elsewhere in the archive
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account