150 HOFME1STER, ON 



By these processes the lower portion of the archegonium 

 becomes a pear-shaped cellular mass, which, at the point 

 where it passes into the upper cylindrical portion (the neck) 

 of the archegonium, surrounds the enlarged cell of the cen- 

 tral string. In most instances the cell of the central string 

 lying immediately above the enlarged cell, exhibits a con- 

 siderable increase of its dimensions (PI. XIX, fig. 5 ; PL 

 XX, fig. 4) ; this is especially remarkable in Sphagnum 

 (PL XVIII, fig. 15). 



Like all the cells of mosses the enlarged cell in question 

 exhibits, from its first appearance, a manifest nucleus. In 

 the very young archegonium the nucleus lies free in the mid- 

 dle of the cell, surrounded on all sides by protoplasm of 

 uniform density (PL XVIII, fig. 14 ; PL XX, figs. 2, 4) ; at a 

 later period, after the separation of the contents of the cell 

 into two parts, viz., the thick coating of the wall, and the 

 less dense fluid contents of the median cavity, the nucleus 

 lies close to the side wall of the cell, surrounded by a thick 

 accumidation of granular protoplasm, which sends forth 

 radiate prolongations over the inner surface of the cell 

 (PL XIX, figs. 5, 6). At this time there is seen under- 

 neath the primary nucleus of the cell, which is still very 

 distinct, a small daughter-cell, occupying about an eighth 

 part of the cell cavity, and having highly refractive con- 

 tents, and a bright nucleus without nucleoli (PL XIX, 

 figs. 5, 6). Contemporaneously with the appearance of 

 this cell, the transverse septa, by which the separate cells 

 of the axile longitudinal string of cells forming the neck 

 of the archegonium are divided from one another, begin 

 to dissolve. Even before these transverse septa have 

 altogether disappeared, even before the dissolution of the 

 transverse septa of the lowest of the cells of the axile 

 string, and therefore before the formation of the canal 

 which traverses the neck of the archegonium longitudinally, 

 the central cell is found to be almost filled by a free 

 spherical cell, which is either suspended freely, or touches 

 the wall of the mother-cell on one side, and which contains 

 a globular central nucleus (PL XVIII, fig. 15; PL XIX, 

 figs. 7, 8, 20; PL XX, figs. 5, 6, 8). The primary 

 nucleus of the cell is no longer present. These circum- 

 stances must lead to the conclusion, that the germinal 



