grains by means of an opening in the sides of the latter; an observation
which I have not succeeded in repeating. I find that the pollen-grains
have been correctly described as extending into a pollen-tube, after
being applied to the surface of the stigma, and it appears to me that
the active granules pass out of the pollen-grains into those tubes.
The O V A R Y adheres firmly to the tube of the calyx, and is often
so twisted, when the flower is about to expand, that its back and the
floral envelopes belonging to it is turned to the front. It consists ot
three perfect carpels, stationed alternately with the stamens, opposite
the petals, and bearing the placentae in their axis, and of three other
pieces alternate with the first, destitute of placentae, and eventually
separating from them when the fruit is ripe. These pieces may be
either regarded as the united margins of the carpels, or as imperfect
carpels; the principal objection to the latter hypothesis consisting in the
intermediate pieces being external with regard to the undoubted carpels.
Dr. Brown takes a different view of the position of the carpels (On
the sexual organs, fyc. in Orchideee and Asclepiadets, p. 12). He considers
them to be stationed opposite the sepals; consequently the intermediate
pieces above described must be in his mind representations
of the dorsal sutures of the carpels, and he must regard each placenta
as of a double nature, half belonging to one carpel and half to another.
To this opinion he appears to have been led both by his own theoretical
views of the general structure of an Orchidaceous flower, and also by
supposing in common with all other Botanists at that time, that placentae
must necessarily alternate with stigmata. But the evidence of Orobanchaceae
shews, as I have elsewhere explained, that in this respect the
theories of Botanists were unsound; and that placentae are beyond all
doubt produced by the axis of carpels as well as by their margins.
The STIGMA is a viscid excavation in front of the anther, and just
below it. In most cases it is quite simple, merely terminating in a glandular
dilatation of the upper margin, called the rostellum. It is lined
with a lax tissue composed of minute ascending jointed hairs, and has
a direct communication with the cavity of the ovary, either open or but
imperfectly closed up. The glandular dilatation, in all Vandeae and
Ophrydeae, and in many genera, separates from the stigma and adheres
to the pollen masses, but it is also, in numerous other genera, at all times
inseparable from it. In Bonatea, in Habenaria, and in some other
genera of Ophrydeae, there are two arms to the upper edge of the
stigma, each arm being channelled for the reception of the caudicula
of a pollen-mass, and terminating in a separable gland; between these
lies a membrane, very variable in size, sometimes merely a connecting
web, sometimes a distinct plicature or lobe, and occasionally fornicate
and extended in the middle into a mucro. In these genera, on the lower
edge of the stigmatic excavation are two processes, long, narrow, channelled,
lined with stigmatic hairs, free at the points, united to the
labellum at the base. Dr. Brown regards the two upper arms and
intervening web of the superior edge of the stigmatic excavation as
belonging to one carpel, and the two imperfect processes adhering to
the base of the labellum, as the styles of the two other carpels; this
view of their nature is the necessary consequence of assuming that the
carpels of which the ovary is composed, are placed opposite the sepals.
But it appears more probable that in such plants the double placentae
are connected with a two lobed style to each carpel; a structure which
would be analogous to what occurs in this and in other Iridaceous
plants, to which Orchidaceae are very nearly allied. Upon this supposition
one arm of each of the fertile styles must be regarded as suppressed,
or united with the contiguous imperfect arm into a plicature or
mucro, and the two sterile processes will belong to the carpel which
is opposite the labellum. That the stigmatic arms are opposite the
petals is manifest in most of the genera where they are found, and
especially in such plants as Disa, Penthea, &c. in which the third and
sterile stigma forms a tubercle at the base of the labellum. That the
connecting web of the fertile arms is of a double nature is also shewn by
its lobed condition in Diplomeris hirsuta, Bonatea flexuosa, and others.
It results from the preceding statements, that the theoretical structure
of an Orchidaceous flower is as follows :—Sepals 3, usually suppressed.
Petals 3, commonly called sepals. Stamens 6, in two series, of which
the outer is sterile, and commonly called petals, and the inner is consolidated
into a column : the two stamens of this series, which are opposite
the so called sepals, being usually abortive. Ovary inferior, composed
of 3 carpels, having double polyspermous placentae in their axis, and