394 HOFMEISTER, ON 



The formation of the archegonium commences by the division 

 by means of a transverse septum of one of the cells of the 

 upper side of the prothallium. This is followed by the 

 division of the upper cell by a longitudinal septum, and the 

 division of the two halves by a septum at right angles to 

 the one last formed and perpendicular to the free outer 

 surface. Each of the four narrow tall cells which are situ- 

 ated above the larger basal cell, is divided by a horizontal 

 septum into two parts of which the under half is usually 

 the lower in height (PL LVIII, fig. 1). The four apical 

 cells of the archegonium generally arch out into short 

 papillae (PL LVIII, fig. 2). By the parting asunder at 

 their edges of contact of the four parallel pairs of cells, a 

 narrow passage is formed, leading to the basal .cell (PL 

 LVIII, figs. I s , 4). In the latter a spherical cell is pro- 

 duced almost filling the mother-cell and rich in finely 

 granular protoplasm. All the narrow cells of the pro- 

 thallium now exhibit distinct nuclei if sufficiently fine sec- 

 tions be taken. The outer walls of the cells of the upper 

 side, especially those of the apical cells of the archegonia 

 appear at this time remarkably thickened (PL LVIII, 

 fig. 2). 



Contemporaneously with the development of the arche- 

 gonia a tissue of wider cells becomes visible spread over 

 the under side of the small-celled portion of the prothallium 

 (PL LVIII, fig. 1). The middle of this cellular mass pro- 

 jects into the unoccupied portion of the inner cavity ; it 

 hangs downwards from the inner wall of the primary spore- 

 membrane for some distance beyond the first-formed por- 

 tion of the prothallium. Its marginal cells repeat the form 

 of that of the older cellular layers ; they are wedge- shaped, 

 and their under side forms a very acute angle with the inner 

 wall of the spore. In S. Martensi a similar large-celled 

 tissue fills the entire cavity of the spore-cell. 



There is only one species, viz. 8. helvetica, in which I have 

 been able to ascertain the behaviour of the small spores 

 after they are set free. In this case however there was no 

 doubt. Pive months after the beginning of March, at 

 which time they were sown upon earth mixed with fine 

 sand and kept continually moist, a large number of very 



