placed opposite the so called petals. Styles 3, opposite the so called
petals, often 2-lobed, and unequally united, those only which are opposite
the lateral so called petals being fertile : all, in most cases, consolidated
so as to be undistinguishable.
Opinions are divided as to the manner in which impregnation
oeeurs in this order. Mr. Bauer adduces a great many facts to show
that it does not take place, as in other plants, by actual contact between
the pollen and the stigmatic secreting surface, but that it is effected by
absorption of fecundating matter by the stigmatic gland from the pollen
through the caudicula. In Tab. III. Fig. 4, Fructification, a supposed
contrivance to effect this purpose by means of foramina in the pouches
of the stigma is represented in Orchis mascula. Plates V, XII, XIII,
XIV, of Fructification, and XVII, XVIII, XIX and XX of Genera,
are particularly intended to illustrate the progressive developement
of the organs of fructification, and Mr. Bauer's opinions regarding
fecundation. The result of which appears to amount to this; that
in an early period of growth there is no communication between the
pollen and stigma; that by degrees this communication is effected
by the extension of the caudicula till it reaches the stigmatic gland,
to which it firmly adheres; up to this time the grains of pollen
are closed up, and the stigmatic surface firm, smooth, dry, and of a
waxy texture ; that after a union is effected between the caudicula of
the pollen masses and the stigmatic glands (which precedes the expansion
of the flower), the pollen grains lose their granular contents, while
the stigmatic glands and surface simultaneously become covered with a
thick mucus; that by the time the flower is expanded, the pollen
is dry and empty of granular matter, and the stigma less mucous
than it was; finally, that, with these changes, alterations take place
in the surface of the stigmatic excavation, which is at first composed
of a loose plexus of cellular tissue, and is eventually broken up into
a stratum of slender utriculi, each containing from 1 to 3 nuclei; these
utriculi are represented as being at first empty, but as presenting, after
the supposed act of impregnation has taken place, the appearance of
grumous matter in their interior. To all this it may be added, that care
seeins to have been taken by nature to prevent the usual contact
between the pollen and stigma, by enclosing the former in an anther,
from which it can only be released by the action of some external
stimulus, such as might be received from a bird or an insect.
On the other hand Dr. Brown, M. Adolphe Brongniart, and others,
suppose that impregnation is effected here as elsewhere by contact
between the pollen and stigma. It is alleged that pollen-tubes are
emitted by the pollen after it has adhered to the stigma, that these tubes
descend the stigmatic canal, and mix themselves among the ovules over
the surface of the placenta^ and that in some cases the pollen-tubes
have been traced into the foramina of the ovules. The latter is a remark
of Dr. Brown's, whose skill and faithfulness as an observer are above all
question.
For a long time I adopted the views of Mr. Bauer, but additional
experience, a careful observation of Orchidaceae in a state of cultivation,
and a verification of some of the facts last described, have caused me to
alter my opinion, to acquiesce in the conclusions of Dr. Brown, and to
regard the phenomena represented by Mr. Bauer as connected with circumstances
not belonging to impregnation. It is now well known that
cultivated Orchidaceee, which rarely fruit if unassisted, may be made to
bear fruit with certainty, if they are artificially impregnated. The effect
of such impregnation is firstly to hasten by many days the decay of the
flower, and secondly, to fill the stigmatic canal with pollen tubes, which
may be traced without difficulty even up to the very maturation of the
fruit.
The determination of this point does not however diminish the value
of Mr. Bauer's observations; it only leaves the facts he describes still to
be accounted for ; and it is a most curious subject of enquiry to investigate
the exact uses of so singular and peculiar a sexual apparatus as
that with which Orchidaceae are furnished.
The SEEDS are generally enveloped by a loose cellular testa, which
is frequently open at the lower end, at the period of maturity. They contain
a nucleus, whose apex is directed towards the base of the seed, and
which is either covered by two extremely thin membranes, frequently