seemed alive. Twenty-two seeds of various kinds were found adhering to
the leaves of plants growing in a state of nature; and of these, though
kept for five months on damp sand, none germinated, some being then
evidently dead.
The Effects of Objects not containing Soluble Nitrogenous Matter.
(16) It has already been shown that bits of glass, placed on leaves,
excite little or no secretion. The small amount which lay beneath the
fragments was tested and found not acid. A bit of wood excited no
secretion; nor did the several kinds of seeds of which the coats are
not permeable to the secretion, and which, therefore, acted like
inorganic bodies. Cubes of fat, left for two days on a leaf, produced
no effect.
(17) A particle of white sugar, placed on a leaf, formed in 1 hr. 10 m.
a large drop of fluid, which in the course of 2 additional hours ran
down into the naturally inflected margin. This fluid was not in the
least acid, and began to dry up, or more probably was absorbed, in 5
hrs. 30 m. The experiment was repeated; particles being placed on a
leaf, and others of the same size on a slip of glass in a moistened
state; both being covered by a bell-glass. This was done to see whether
the increased amount of fluid on the leaves could be due to mere
deliquescence; but this was proved not to be the case. The particle on
the leaf caused so much secretion that in the course of 4 hrs. it ran
down across two-thirds of the leaf. After 8 hrs. the leaf, which was
concave, was actually filled with very viscid [page 388] fluid; and it
particularly deserves notice that this, as on the former occasion, was
not in the least acid. This great amount of secretion may be attributed
to exosmose. The glands which had been covered for 24 hrs. by this
fluid did not differ, when examined under the microscope, from others
on the same leaf, which had not come into contact with it. This is an
interesting fact in contrast with the invariably aggregated condition
of glands which have been bathed by the secretion, when holding animal
matter in solution.
(18) Two particles of gum arabic were placed on a leaf, and they
certainly caused in 1 hr. 20 m. a slight increase of secretion. This
continued to increase for the next 5 hrs., that is for as long a time
as the leaf was observed.
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