_.

Many of these cases, and others that might be cited, are probably
instances of frondescence or phyllody (see p. 241).

=Chromatism.=--This term is here intended to apply specially to those
cases in which any organ of a plant assumes a colour approximating to
that of the petals, or in which the normal green is replaced by tints of
some other colour. To a certain extent the change in question is the
same as that spoken of under the head of petalody (see p. 283), but
there are cases in which, while the ordinary situation and form are
those of leaves, the coloration is that of the petals. Such was the case
in the _Gesnera_ mentioned by Morren (see p. 88), and in which a leaf
occupied the position of an inflorescence, and became brightly coloured.
In tulips the presence of a highly coloured leaf on the flower-stalk,
below the flower, is not uncommon. So also the bracts or leaves below
the perianth in _Anemone coronaria_ and _hortensis_ not unfrequently
assume the coloration usually confined to the parts of the perianth. A
similar illustration has presented itself, as this sheet is passing
through the press, in which two of the leaflets of the compound leaf of
a rose were brightly coloured like the petals, the others being of
their ordinary green colour.

The occurrence of coloured bracts, as in _Poinsettia_, _Bougainvillea_,
&c., is very common under natural conditions, and need not here be
further alluded to.

Increased intensity of colour often accompanies teratological changes;
an instance has just been alluded to in the _Gesnera_; the feather
hyacinth, _Muscari comosum_, furnishes another illustration, the
adventitious pedicels being brightly coloured.

In fasciated stems, also, of herbaceous plants, it not unfrequently
happens that the upper portions of the stem are brightly coloured.

The occurrence of flowers or fruits of different colours on the same
plant, or even in the same cluster, is a phenomenon which does not come
within the scope of the present book; the reader may, however, be
referred to the excellent summary on this subject published by Mr.
Darwin in his work on the 'Variation of Animals and Plants under
Domestication.'

FOOTNOTES:

[372] These deviations are treated of under the head of alterations of
form, because they are not, in a teratological point of view, of
sufficient importance to demand a specific heading, while they appeal to
the sight in the same way as the deviations from the cu