in a quite subordinate manner. All
these modifications follow from the relative position and inter-action
of the parts; and it can hardly be doubted that if all the flowers and
leaves on the same plant had been subjected to the same external and
internal condition, as are the flowers and leaves in certain positions,
all would have been modified in the same manner.

In numerous other cases we find modifications of structure, which are
considered by botanists to be generally of a highly important nature,
affecting only some of the flowers on the same plant, or occurring on
distinct plants, which grow close together under the same conditions. As
these variations seem of no special use to the plants, they cannot
have been influenced by natural selection. Of their cause we are quite
ignorant; we cannot even attribute them, as in the last class of cases,
to any proximate agency, such as relative position. I will give only
a few instances. It is so common to observe on the same plant, flowers
indifferently tetramerous, pentamerous, etc., that I need not give
examples; but as numerical variations are comparatively rare when the
parts are few, I may mention that, according to De Candolle, the flowers
of Papaver bracteatum offer either two sepals with four petals (which
is the common type with poppies), or three sepals with six petals. The
manner in which the petals are folded in the bud is in most groups a
very constant morphological character; but Professor Asa Gray states
that with some species of Mimulus, the aestivation is almost as
frequently that of the Rhinanthideae as of the Antirrhinideae, to which
latter tribe the genus belongs. Aug. St. Hilaire gives the following
cases: the genus Zanthoxylon belongs to a division of the Rutaceae with
a single ovary, but in some species flowers may be found on the same
plant, and even in the same panicle, with either one or two ovaries.
In Helianthemum the capsule has been described as unilocular or
tri-locular; and in H. mutabile, "Une lame PLUS OU MOINS LARGE,
s'etend entre le pericarpe et le placenta." In the flowers of Saponaria
officinalis Dr. Masters has observed instances of both marginal and free
central placentation. Lastly, St. Hilaire found towards the southern
extreme of the range of Gomphia oleaeformis two forms which he did
not at first doubt were distinct species, but he subsequently saw them
growing on the same bush; and he then adds, "Voila donc dans un meme
individu