132 MOSSES AND FERNS CHAP. 



separation of the cells is accompanied by a mucilaginous 

 change in their outer layers. 



The first account of the archegonium was given by Hof- 

 meister, who, however, overlooked the peripheral cells and only 

 saw the axial row. Later Janczewski (2) showed that Antho- 

 ceros did not differ essentially in the development of the 

 archegonium from the other Hepaticse, and his observations 

 were confirmed by the later researches of Leitgeb and Wald- 

 ner (2). The formation of archegonia does not begin until 

 the older antheridia are mature, and very often, especially in 

 A. Pearsoni, few or no antheridia were found on the plants 

 with well-developed archegonia. After the formation begins, 

 each dorsal segment gives rise to an archegonium, so that they 

 are arranged in quite regular rows, in acropetal order. After 

 the transverse wall by which the segment is divided into an 

 inner and an outer cell is formed, the outer cell becomes at 

 once the mother cell of the archegonium, much as in Aneura. 

 In this cell next arise three vertical intersecting walls, by 

 which a triangular (in cross-section) cell is cut out as in the 

 other Hepaticse. Sometimes it looks as if one of these walls 

 was suppressed, but even in such cases the triangular form of 

 the central cell is evident. The main difference between the 

 archegonium at this stage in Anthoceros and the Hepaticse 

 lies in the complete submersion of the archegonium rudiment 

 in the former. In this respect Aneura, where the base of the 

 archegonium is confluent with the cells of the thallus, offers an 

 interesting transition between the other Hepaticse, where the 

 base of the archegonium is entirely free, and Anthoceros. 



The archegonium rudiment divides into two tiers as in the 

 other Liverworts, and the peripheral cells divide longitudinally, 

 and the neck shows the six vertical peripheral rows although 

 it is completely sunk. Later, the limits of the neck become 

 often hard to determine, although by later divisions the central 

 cell is surrounded by a pretty definite layer of cells. The 

 axial cell divides into two of nearly equal size, but the inner one 

 soon increases in breadth more than the upper one. The latter 

 divides again by a transverse wall into an outer cell corre- 

 sponding to the cover cell of the ordinary hepatic archegonium, 

 the other to the primary neck canal cell. The cells of this cen- 

 tral row soon become clearly different from the other through 

 their more granular contents. The lower cell grows much 



