INTRODUCTION. 343 



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 Hepaticae 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 Marchantiese) ; in the 

 foliose Jungermanniese 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 

 Sphagnum. 



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 Jungermannieae and in Mosses 

 several archegonia are commonly surrounded by an investment formed of leaves 

 which is termed the PerichcBtium ; 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 perichaetium, there 

 is also often in Hepaticae (but not in Mosses) a so-called Pertgynium, 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 



