had their contents much shrunk, and some were almost empty. In only a
few cases were the pollen-tubes emitted. There could be no doubt that
the secretion had penetrated the outer coats of the grains, and had
partially digested their contents. So it must be with the gastric juice
of the insects which feed on pollen, without masticating it.* Drosera
in a state of nature cannot fail to profit to a certain extent by this
power of digesting pollen, as innumerable grains from the carices,
grasses, rumices, fir-trees, and other wind-fertilised plants, which
commonly grow in the same neighbourhood, will be inevitably caught by
the viscid secretion surrounding the many glands.
Gluten. This substance is composed of two albuminoids, one soluble, the
other insoluble in alcohol.** Some was prepared by merely washing
wheaten flour in water. A provisional trial was made with rather large
pieces placed on two leaves; these, after 21 hrs., were closely
inflected, and remained so for four days, when one was killed and the
other had its glands extremely blackened, but was not afterwards
observed.
* Mr. A.W. Bennett found the undigested coats of the grains in the
intestinal canal of pollen-eating Diptera; see Journal of Hort. Soc.
of London, vol. iv. 1874, p. 158.
** Watts Dict. of Chemistry, vol. ii. 1872, p. 873. [page 118]
Smaller bits were placed on two leaves; these were only slightly
inflected in two days, but afterwards became much more so. Their
secretion was not so strongly acid as that of leaves excited by casein.
The bits of gluten, after lying for three days on the leaves, were more
transparent than other bits left for the same time in water. After
seven days both leaves re-expanded, but the gluten seemed hardly at all
reduced in bulk. The glands which had been in contact with it were
extremely black. Still smaller bits of half putrid gluten were now
tried on two leaves; these were well inflected in 24 hrs., and
thoroughly in four days, the glands in contact being much blackened.
After five days one leaf began to re-expand, and after eight days both
were fully re-expanded, some gluten being still left on their discs.
Four little chips of dried gluten, just dipped in water, were next
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