such are seized on not only by the morphologist, but by
the systematic botanist, who finds in them the characters by which he
may separate one group from another. Thanks to the labours of those
observers who have devoted their attention to that difficult but most
important branch of study, organogeny, or the investigation of the
development of the various organs, and to the researches of the students
of comparative anatomy or morphology, the main principles regulating the
arrangement and form of the organs of flowering plants seem to be fairly
well established, though in matters of detail much remains to be
cleared up, even in such important points as the share which the axis
takes in the construction of the flower and fruit, the nature of the
placenta, the construction of the ovules, and other points.

The facts already known justify the adoption of a standard or typical
arrangement as just mentioned. The intrinsic value of this type is shown
by the facility with which all varieties of form or arrangement may be
explained by reference to certain modifications of it. It must, however,
be considered as an abstraction, and should be looked on in the light
rather of a scaffolding, which enables us to see the building and its
several parts, than of the edifice itself, but which latter, from our
imperfect knowledge and limited powers, we could not see without some
such assistance.

The typical form may be, hypothetically at least, considered as the
primitive one transmitted by hereditary descent from generation to
generation, and modified to suit the requirements of the individual, or
in accordance with circumstances. If it be borne in mind that it is but
an artificial contrivance, more or less true--a means to an end, and not
the end itself--no harm will arise from its employment; and as knowledge
increases, or as circumstances demand, the hypothetical type can be
replaced by another more in accordance with the actual state of science.

Teratological changes in the arrangement of organs depend upon arrest of
growth, as when parts usually spirally arranged remain verticillate,
owing to the non-development of the internodes, or to excessive growth,
or development; but in many instances it is impossible, without
studying the development of the malformed flower, to ascertain whether
the altered arrangement is due to an excessive or to a diminished
action. Practically, however, it is of comparatively little importance
to kn