ht
difference in the nature of the poison suffices to produce widely different
results;--and lastly, as we know that the chemical compounds secreted by
plants are eminently liable to be modified by changed conditions of life,
we may believe it possible that various parts of a plant might be modified
through the agency of its own altered secretions. Compare, for instance,
the mossy and viscid calyx of a moss-rose, which suddenly appears through
bud-variation on a Provence-rose, with the gall of red moss growing from
the inoculated leaf of a wild rose, with each filament symmetrically
branched like a microscopical spruce-fir, bearing a glandular tip and
secreting odoriferous gummy matter.[708] Or compare, on the one hand, the
fruit of the peach, with its hairy skin, fleshy covering, hard shell and
kernel, and on the other hand one of the more complex galls with its
epidermic, spongy, and woody layers, surrounding tissue loaded with starch
granules. These normal and abnormal structures manifestly present a certain
degree of resemblance. Or, again, reflect on the cases above given of
parrots which have had their plumage brightly decorated through some change
in their blood, caused by having been fed on certain fishes, or locally
inoculated with the poison of a toad. I am far from wishing to maintain
that the moss-rose or the hard shell of the peach-stone or the bright
colours of birds are actually due to any chemical change in the sap or
blood; but these cases of galls and of parrots are excellently adapted to
show us how powerfully and singularly external agencies may affect
structure. With such facts before us, we need feel no surprise at the
appearance of any modification in any organic being.

I may, also, here allude to the remarkable effects which parasitic
fungi sometimes produce on plants. Reissek[709] has described a
Thesium, affected by an Oecidium, which was greatly modified, and
assumed some of the {285} characteristic features of certain allied
species, or even genera. Suppose, says Reissek, "the condition
originally caused by the fungus to become constant in the course of
time, the plant would, if found growing wild, be considered as a
distinct species or even as belonging to a new genus." I quote this
remark to show how profoundly, yet in how natural a manner, this plant
must have been modified by the parasitic fungus.

_Facts and Considerations opposed to the belief th