1915] HUTCHINSON— PELLIA EPIPHYLLA 135 



the successive divisions follow an antheridial sequence; if, how- 

 ever, the wall is inclined and somewhat removed from the central 

 position, the cell divisions which follow are similar to those of a 

 developing archegonium. In the former case the vertical wall is 

 followed by a curved wall on either side, which cuts the vertical 

 wall as shown in figs. 7 and 8. Two similar walls, rotated about 

 the central axis through an angle of go° (figs. 8, q), complete the 

 separation of the peripheral region from the central spermatogenous 

 region. The first two of these walls may be nearly parallel at the 

 base (fig. 7), or they may be at right angles; similarly the second 

 pair. Such an antheridium is characteristic of the Jungermanniales. 



Occasionally the outer cell, mentioned above, is divided into 

 quadrants by walls at right angles to the vertical wall (figs. 10, 11), 

 in which case four wall cells are cut off by periclinal divisions, 

 giving also four spermatogenous cells. The process is similar to 

 that characteristic of Sphaerocarpus or Marchantiales. 



Fig. 14 illustrates the result of a combination of these two 

 methods of development. In fig. 1 5 is shown a double antheridium ; 

 the two halves have become completely separated by the vertical 

 division and each has developed independently. The process may 

 be compared to the characteristic development of the double 

 antheridia of Anthocerotales. 



When the first wall formed in the outer cell is inclined and 

 somewhat removed from the median position, it is followed by a 

 second and a third wall, each of which is similarly placed, but 

 revolved with respect to each other through an angle of 1 20 about 

 the vertical axis (figs. 17, 18, 26, 27, 28). A transverse wall divides 

 the central cell into the cap cell and the spermatogenous initial 

 (fig. 19). The characteristic archegonial development is followed 

 until the massive spermatogenous group begins to be formed (figs. 

 22, 28), instead of the axial row. 



Occasionally this critical third wall of the antheridium is inclined 

 inward instead of outward, as described above (fig. 23). Two 

 walls similarly inclined complete the separation of the peripheral 

 region from the central spermatogenous initial (figs. 24, 25). This 

 form is similar to that last described with the exception of the incli- 

 nation of the walls and the resulting lack of the cap cell. 



