the whole form is altered and
depauperated. Degeneration, thus, is the result not so much of a
deficiency in growth as of a perversion of development.

Under natural, _i.e._ habitual circumstances, the formation of pappus
in place of a leafy calyx may be considered as an illustration of
degeneration. It is evident, however, that no very decided line of
demarcation can be drawn between cases of perversion and of arrest of
development.

=Formation of scales.=--These may be mere epidermal excrescences, or
they may be the abortive rudiments of leaves. Of this latter nature are
the "cataphyllary" leaves which invest the root stocks of so many
perennial plants, the perulae of leaf-buds, or the paleae on the common
receptacle of composite flowers. Other illustrations of a like character
are to be met with in the membranous scales that represent leaves in
_Ruscus_, _Asparagus_, _Pinus_, &c. Similar productions are met with
within the flower, where they may occur as the representatives of
sepals, petals, stamens, or pistils, or as mere excrescences. (See
Enation.) Whole families of plants, _e.g._ _Sapindaceae_, are
characterised by the presence of these organs, which are often of great
interest to the morphologist as indicating the true symmetry of the
flower, while they have acquired fresh importance since the publication
of Mr. Darwin's work on the 'Origin of Species,' wherein we are taught
to regard these rudiments as, in many cases, vestiges of organs that
were more completely developed in the progenitors of the present race of
plants, and the exercise of whose functions, from some cause or other,
having been rendered impossible, the structures become, in process of
time, proportionately stunted.

Thus, in dioecious plants we frequently find traces of stamens in the
female flowers, and rudiments of the pistil in the male flower,
indicating, according to the Darwinian hypothesis, that the ancestors of
these plants were hermaphrodite (see Heterogamy).

Mr. Darwin has also shown that, in some cases, the utmost degree of
fertility is attained, not from the action of the pollen on the stigma
of the same flower, but on the influence of the male element of one
blossom upon the female organs of another flower on another individual
plant.

Hence, in such plants there is a tendency to a separation of the sexes,
while, from what has been before stated, it might be expected that
rudiments of the male or female organs would be foun