HEPA TICM. 
349 
or dioeciously. There is a general tendency in the thalloid Hepaticae for the 
sexual organs to be depressed into hollows by overarchings of the surrounding tissue, 
often opening externally by only a narrow mouth. An example of this is given in 
Fig. 235. 
In the foliose Jungermannieae the origin of the antheridia and archegonia is 
very various, and they are also enveloped in different ways. Further reference will 
be made to this in describing the different families. 
The antheridium consists, in the mature state, of a pedicel surmounted by 
a globular or ellipsoid body; in those which are imbedded in the tissue the former 
is usually short, in the free forms it is long, and com- 
posed of from one to four rows of cells. The body 
of the antheridium consists of a wall formed of a single 
layer of cells containing chlorophyll ; the whole of the 
space enclosed by it is densely filled by the mother- 
cells of the antherozoids ; their escape is occasioned 
by the access of water and separation of the cells of 
the wall at the apex ; sometimes, as in Fossombronia, 
these cells even fall away from one another. The 
small mother-cells of the antherozoids which escape 
.in great numbers, separate in the water; the anthero- 
zoids become free, and have the appearance of slender 
threads curved spirally from one to three times, and 
provided at the anterior end with two long very fine 
cilia, by means of which they move in the water with 
a rotating motion. Usually they drag after them at 
the posterior end a small delicate vesicle, the origin of 
which Strasburger traces to the central vacuole in the protoplasm of the mother-cell, 
in the periphery of which the antherozoid has been formed. 
The succession of cell-divisions in the formation of the antheridia has been 
shown by the researches of recent observers to present great diversities in the 
different genera; they agree, however, in the antheridium always making its first 
appearance as a papilliform swelling of a cell from which it is separated by a 
septum. This papilla thus detached again divides into a lower and an upper cell, 
the former of which produces the pedicel, the latter the body of the antheridium 
(parietal layer and mother-cells of the antherozoids). 
The succession of cell-divisions in the formation of the archegonia, from the 
observations of Janczewski^, Leitgeb, Kny, and Strasburger, appeal's to be essentially 
the same in the different families, even, mutatis mutandis, among the Anthoceroteae. 
It is certain that the archegonium, like the antheridium, makes its first appearance 
as a simple papilla, which, in the case of the first archegonium of a receptacle 
of Radula, is itself the apical cell of the shoot. This papilla is shut off by a septum, 
and, in Riccia^ is at once the mother-cell of the whole archegonium : in the other 
Hepaticae it is divided by a second septum into two cells, the lower one of which 
Fig. 235. — Anterior margin of tlie youngs 
antheridial disc of Maj-chantia polynior- 
plia; a the growing margin; a, a, a the 
antlieridia in different stages of develop- 
ment ; sp the stomata above tlie air-cavities 
between the antheridia (after Hofmeister, 
X 300). 
^ [Janczewski has made a series of comparative researches into the development of the arche- 
gonium of Muscineae, Bot. Zeitg. 1872, p. 869 et seq.] 
