Petroselinum_;[421] Ehrenberg to
one in the marigold (_Calendula_);[422] Reinsch to an analogous
appearance in the beech (_Fagus_), associated with a union of the
margins of two out of the three cotyledons, and of those of two out of
the three leaves next adjacent.[423] This fusion seems frequently to
accompany increase in the number of cotyledons. It was so in the
_Correa_, and in the _Crataegus_ previously mentioned. Some of these
cases may be accounted for by chorisis or by a cleavage of the original
cotyledons, as happens, according to Duchartre,[424] in some Coniferae,
which he considers to be improperly termed polycotyledonous. Whether
this holds good in the Loranths, where (_Nuytsia_, _Psittacanthus_) an
appearance of polycotyledony exists, is not stated. In the case of the
rue (_Ruta_) figured by M. A. de Jussieu[425] this splitting of one
cotyledon into two is sufficiently evident, as is also the case in the
sycamore (_Acer pseudo-platanus_), seedlings of which may often be met
with divided cotyledons.

In other instances a fusion of two embryo plants may give rise to a
similar appearance, as in the _Euphorbia_ and _Sinapis_ found by M.
Alph. de Candolle (see _ante_, p. 56).

=Pleiotaxy or multiplication of whorls.=--In the preceding section
notice has been taken of the increased number of parts in a single
whorl, but an augmentation of the number of distinct whorls is still
more frequently met with. Many of the so-called double flowers owe their
peculiarity to this condition. The distinction between the two modes in
which the parts of the flower are increased in number has been pointed
out by Engelmann, Moquin, and others, and the two seem to require
distinctive epithets; hence the application of the terms polyphylly and
pleiotaxy, as here proposed.

=Pleiotaxy in the bracts.=--An increase in the number of bracts has been
met with very constantly in a species of _Maesa_, and in a peculiar
variety of carnation, called the wheat-ear carnation.[426] In some of
these cases the increase in the number of bracts is attended by a
corresponding suppression in the other parts of the flower. Such a
condition has been frequently met with in _Gentiana Amarella_, where the
bracts are increased in number, coloured purple, and destitute of any
true floral organs. A similar condition exists in some varieties of
_Plantago major_ (var. _paniculata_), as has been previously stated, p.
109.

[Illustration: FIG. 187.--Wheat-ea