l dwarf varieties of
plants (var. _nanae_), or those in which the leaves or flowers are
smaller than usual (var. _parvifoliae_, v. _parviflorae_), are truly
regarded as variations, and not as malformations properly so called.

Atrophy is partial and special in its operation, nanism is general.

Under ordinary circumstances atrophy is exemplified by the presence of
rudimentary or imperfect organs, as, for instance, in _Pentstemon_,
_Scrophularia_, &c., where one stamen is atrophied.

For convenience sake atrophy may be divided into abortion and
degeneration, the first including cases where, from arrest of
development occurring at an early stage, organs are present; but in a
much smaller and more rudimentary condition than usual, their form and
general appearance, except so far as regards their dimensions, not being
materially altered. On the other hand, in cases of degeneration,
development is not entirely checked, but rather perverted, so that not
only the dimensions are lessened, but the form is altered.

CHAPTER I.

ABORTION.

The sense in which this term is here understood has been explained in
the preceding paragraph. It is only necessary to say further, that cases
of abortion are to be distinguished from those of suppression, on the
one hand, and those of degeneration on the other. In suppression there
is from the first an absolute deficiency of a particular organ. In
degeneration the part is present, but in a diminished and perverted
condition. In abortion it exists, but in a stunted and dwarfed, but not
otherwise permuted state.

=Abortion of axile organs.=--When the main stem is arrested in its
growth, the habit and general appearance of the plant are materially
altered, as in the so-called stemless plants, _plantae acaules_. In these
the internodes are so slightly developed that the leaves are closely
crowded in tufts or rosettes. When this shortening of the stem
(acaulosia) occurs, without other considerable change in other organs,
the deviation is classed under the head of variation rather than of
monstrosity; and, indeed, in very many plants, this arrested growth of
the axis is the rule rather than the exception. When occurring in an
abnormal manner, atrophy of the stem is most frequently attended by
other more or less grave alterations in other structures; thus
Moquin-Tandon[522] cites an instance of _Camphorosma monspeliaca_,
wherein the stems presented the form of very short, hard, woody