of an
_Iris_.[476]

Orchids seem peculiarly liable to the decrease in the number of their
floral organs. Prillieux[477] mentions a flower of _Cattleya
amethystina_ wherein each whorl of the perianth consisted of two
opposite segments.

The same observer has put on record instances of a similar kind in
_Epidendrum Stamfordianum_. In one flower of the last-named species the
perianth consisted of one sepal only, and one lip-like petal placed
opposite to it.[478] Morren[479] describes a flower of _Cypripedium
insigne_, in which there were two sepals and two petals. Of a similar
character was the flower found by Mr. J. A. Paine, and described in the
following terms by Professor Asa Gray in the 'American Journal of
Science,' July, 1866:--"The plant" (_Cypripedium candidum_) "bears two
flowers: the axillary one is normal; the terminal one exhibits the
following peculiarities. The lower part of the bract forms a sheath
which encloses the ovary. The labellum is wanting; and there are two
sterile stamens, the supernumerary one being opposite the other, _i.e._
on the side of the style where the labellum belongs. Accordingly the
first impression would be that the labellum is here transformed into a
sterile stamen. The latter, however, agrees with the normal sterile
stamen in its insertion as well as in shape, being equally adnate to the
base of the style. Moreover, the anteposed sepal is exactly like the
other, has a good midrib and an entire point. As the two sterile stamens
are anteposed to the two sepals, so are the two fertile stamens to the
two petals, and the latter are adnate to the style a little higher than
the former. The style is longer than usual, is straight and erect; the
broad, disciform stigma therefore faces upwards; it is oval and
symmetrical, and a light groove across its middle shows it to be
dimerous. The placentae, accordingly, are only two. The groove on the
stigma and the placentae are in line with the fertile stamens.

Here, therefore, is a symmetrical and complete, regular, but dimerous
orchideous flower, the first verticil of stamens not antheriferous, the
second antheriferous, the carpels alternate with these; and here we have
clear (and perhaps the first direct) demonstration that the orchideous
type of flower has two stamineal verticils, as Brown always insisted."

[Illustration: FIG. 198.--Regular dimerous flower of _Calanthe
vestita_.]

[Illustration: FIG. 199.--Regular dimerous flower of _Odo