116 HOFMEISTER, ON 



and nearer to its centre, arranged in radial double rows 

 (PL XV, fig. 11). A phenomenon, of which traces are 

 seen in Rebouillia, is very strongly marked in Marchantia : 

 the underside of the margin of the receptacle is developed 

 at a very early period between each two archegonia into a 

 process extending downwards for a considerable distance, 

 whose form gradually passes from that of a hemispherical 

 wart to that of a long, cylindrical prolongation, curved 

 slightly inwards, with deep, longitudinal furrows on the 

 under side, in which rootlets lie concealed. 



The archegonia of Marchantia polymorpka are large-celled, 

 the ventral portion being remarkably swollen at an early 

 period. A single layer of flat, tabular cells surrounds the 

 proportionably large central cell of the ventral portion, 

 which is attached almost immediately to the under side of 

 the receptacle. The neck of the archegonium, which in its 

 earliest youth is curved strongly upwards (PL XV, fig. 12), 

 is pointed directly downwards at the time when the apex 

 opens (PL XV, figs. 13, 14). 



After the parting asunder of the cells of the apex, the 

 central cell of the ventral portion of the impregnated arche- 

 gonium enlarges very considerably. A free, oval cell entirely 

 fills its inner cavity. Its large central nucleus is very 

 plainly distinguishable as a clear vesicle in the thick 

 granular mucilage (PL XV, figs. 13, 14). The transforma- 

 tion of this cell into the rudimentary fruit is introduced by 

 the appearance of a much inclined longitudinal septum 

 PI. XV, fig. 15). The septa, which are formed at a later 

 period in the apical cell, diverge only very slightly from the 

 longitudinal axis of the fruit. T have but seldom and only 

 imperfectly succeeded in detaching the young rudimentary 

 fruit. It remains for some time spherical ; its cells soon 

 become very small by repeated cell- divisions. 



After the first divisions of the primary cell of the rudi- 

 mentary fruit, the cells of the young calyptra double them- 

 selves by the formation of septa parallel to the outer surface. 

 A special covering has at an earlier period been formed 

 close round each impregnated archegonium. The ring of 

 bells of the under side of the receptacle which surrounds the 

 case of the archegonium protrudes outwards ; the protru- 



