INTRODUCTION. 
The sexual organs are Anther idia and Archegonia. The mature antheridium is 
a body with a longer or shorter stalk, of a spherical, ellipsoidal, or club-shaped form, 
the outer layer of its cells forming a sac-like wall, while each of the small and very 
numerous crowded cells enclosed within it developes an antherozoid. The anther- 
ozoids are freed by the rupture of the wall of the antheridium at the apex ; they 
are spirally coiled threads thicker at the posterior and tapering to a fine point at 
the anterior end, at which are placed two long fine cilia, the vibrations of which 
cause their motion. The female organs, which since the time of Bischoff have been 
called archegonia, are, when in a condition capable of being fertilised, flask-shaped 
bodies bulging from a narrow base and prolonged into a long neck. The wall 
of the ventral portion encloses the central cell, the inferior and larger part of which 
forms the oosphere. Above this begins a row of cells which passes through the 
neck in an- axial direction, and is continued as far as the cells which form the 
so-called ' Stigma.' The cells of this axial row become broken up before fertili- 
sation, and transformed into mucilage which finally swells up and forces apart the 
four stigmatic cells. In this manner an open canal is formed, which leads down 
as far as the oosphere, and enables the antherozoids to enter it. 
The great diversity in the origin of the sexual organs of Muscinese is of 
great importance. In the thalloid Hepaticse these organs arise behind the 
growing apex from the superficial cells of the thallus or of the prostrate thalloid 
stem, or on specially metamorphosed branches (as in the Marchantie8e) ; in the 
foliose Jungermannieae and in the Mosses not only the antheridia but also the 
archegonia may be formed from the apical cell of the shoot or from segments 
of it; in this case they may take the place of leaves, or of lateral shoots, or 
even of hairs. Thus the antheridia appear as metamorphosed trichomes in the 
axils of the leaves of Radula, as metamorphosed shoots in Sphagnum, as apical 
structures and also as metamorphosed leaves in Fontinalis, In the same manner 
the first archegonium of the fertile shoots of Andrecea and Radula arises from the 
apical cell, the later ones from its last segments ; and this is probably the case in 
Sphagnuni. 
The antheridia and archegonia are usually produced in great numbers in close 
proximity; in the thalloid forms of the Hepaticae they are generally enveloped 
by later outgrowths of the thallus ; in the foliose Jungermanniese and in Mosses 
several archegonia are commonly surrounded by an investment formed of leaves 
which is termed the Perichcßtium ; in Mosses the antheridia (with sometimes some 
archegonia) are usually borne in this manner also, while the antheridia of the 
Jungermannieae and of Sphagnum stand alone. Very commonly, especially in the 
foliose kinds, Paraphyses, i.e. articulated threads or narrow leaf-like plates of cells, 
are developed by the side of the sexual organs. Besides the perichsetium, there 
is also often in Hepaticae (but not in Mosses) a so-called Perigyniwu, which grows 
as an annular wall at the base of the archegonia, and finally surrounds them as an 
open sac. 
The Asexual Generation (Sporophore), the Sporogonium, arises in the archego- 
nium from the fertilised oosphere (oospore). It first developes by repeated cell- 
divisions into an ovoid embryo, growing at the end turned towards the neck of 
the archegonium, that is, the apex. Its final form is very different in different 
