GAMETOPHYTE. 37 



from the surface of the cushion they divide each into a row of cells (fig's. 

 208-213). The neck, therefore, consists of four rows of cells (figs. 213, 

 220-222), two anterior and two posterior. The divisions always occur in 

 the uppermost or next to uppermost members (fig-. 210). At maturity 

 the neck bends over strongly away from the growing- point of the pro- 

 thallus (fig's. 207, 211, 219). In relation to this we find in each of the two 

 rows of cells of the neck on the convex side two cells more than on the 

 concave side (4 and 6, or 5 and 7). 



Meanwhile the central cell has cut off a "neck canal-cell" (fig's. 209, 

 210), which pushes up in the axis of the neck. It acquires two nuclei 

 (fig-. 215), rarely three (fig- 218). Another division in the central cell 

 cuts off the "ventral canal-cell," lying- at the base of the neck (fig's. 216, 

 217, 218). The largfe remainder is the eg-g--cell. As the archeg-onium 

 matures the neck enlargfes and becomes swollen near the end (fig-. 219). 

 The canal-cells deg-enerate into an amorphous mass, the central parts of 

 which stain deeply with haematoxylin. At this time also a distinct venter 

 wall is formed around the egg by divisions in all the prothallial cells sur- 

 rounding- it (figs. 219, 223, 224). To recapitulate, the archeg-onium as a 

 whole is made up from two sources the neck, canal-cells, egg, and four 

 basal cells of the venter are all derived from the original cubical arche- 

 g-onium mother-cell; the side walls of- the venter are derived from all the 

 neighboring- prothallial cells. 



TABLE 8. Development of archegonium. 



neck cell 4 neck cells-4 rows of neck cells 



Mother / 



cell \ /neck canal cell;- neck canal cell, 2 or 3 nuclei 



interior cell-^- central cell/ 



\ /ventral canal cell 



central cell<" 



ovum 



sal cell 4 basal cells base of venter wall 

 Surrounding cells of prothallus form side walls of venter. 



When the archegonium is wholly mature, the uppermost four or eigfht 

 neck-cells break apart, leaving- a wide-open mouth (figs. 220, 224). 

 Through this a transparent mucilaginous substance exudes, and may 

 stream out for a distance several times the length of the archegonium 

 (fig. 224). In this substance spermatozoids gather in great numbers. 

 As a sperm enters the mucilage its movements become slower, and it 

 changes from a short, stout helix to a long, slender one with more turns. 

 The vesicle attached to its posterior end is twisted off by the resistance of 

 the mucilage and floats away. The sperms swarm into the neck and 

 make their way down towards the egg, which becomes pointed as though 

 reaching out to receive them (fig. 223). The lower part of the neck is so 

 constricted (fig. 222) that the sperms have to become nearly straight to 

 get through, but many succeed in doing so. 



