Chitine. The chitinous coats of insects naturally captured by the
leaves do not appear in the least corroded. Small square pieces of the
delicate wing and of the elytron of a Staphylinus [page 125] were
placed on some leaves, and after these had re-expanded, the pieces were
carefully examined. Their angles were as sharp as ever, and they did
not differ in appearance from the other wing and elytron of the same
insect which had been left in water. The elytron, however, had
evidently yielded some nutritious matter, for the leaf remained clasped
over it for four days; whereas the leaves with bits of the true wing
re-expanded on the second day. Any one who will examine the excrement
of insect-eating animals will see how powerless their gastric juice is
on chitine.
Cellulose. I did not obtain this substance in a separate state, but
tried angular bits of dry wood, cork, sphagnum moss, linen, and cotton
thread. None of these bodies were in the least attacked by the
secretion, and they caused only that moderate amount of inflection
which is common to all inorganic objects. Gun-cotton, which consists of
cellulose, with the hydrogen replaced by nitrogen, was tried with the
same result. We have seen that a decoction of cabbage-leaves excites
the most powerful inflection. I therefore placed two little square bits
of the blade of a cabbage-leaf, and four little cubes cut from the
midrib, on six leaves of Drosera. These became well inflected in 12
hrs., and remained so for between two and four days; the bits of
cabbage being bathed all the time by acid secretion. This shows that
some exciting matter, to which I shall presently refer, had been
absorbed; but the angles of the squares and cubes remained as sharp as
ever, proving that the framework of cellulose had not been attacked.
Small square bits of spinach-leaves were tried with the same result;
the glands pouring forth a moderate supply of acid secretion, and the
tentacles remaining inflected for three days. We have also seen that
the delicate coats of pollen grains are not dissolved by the secretion.
It is well known that the gastric juice of animals does not attack
cellulose.
Chlorophyll. This substance was tried, as it contains nitrogen. Dr.
Moore sent me some preserved in alcohol; it was dried, but soon
deliquesced. Particles were placed on four leaves; after 3 hrs. the
secretion was acid; after 8 hrs. there was a good deal of inflection,
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