1920] HAUPT—FOSSOMBRONIA 325 



then divides the outer cell into equal segments, forming a primary- 

 stalk cell and a primary antheridial cell (fig. 10). The next 

 division is vertical in the antheridial cell, and is usually followed 

 by a similar division in the stalk cell (fig. 11), which may be parallel 

 with or at right angles to the vertical wall in the antheridial cell 

 (figs. 13, 14). Two periclinal walls then appear in the antheridial 

 cell (figs. 13, 14); their relation to the first vertical wall may best 

 be seen in a cross-sectional view (fig. 15). Two additional periclinal 

 walls, which come in at right angles to the first two, complete 

 the peripheral layer of 4 primary wall cells, which are thus separated 

 from the 2 central spermatogenous cells (fig. 15). The cell contents 

 of the primary spermatogenous cells assume a much darker stain 

 than the contents of the primary wall cells or the cells of the 

 stalk; in no cases were periclinal walls seen in the stalk cell. Thus 

 there can be no doubt that the antheridium develops according to 

 the usual method found among the anacrogynous Jungerman- 

 niales, and not as Humphrey has described for F. longiseta. 



Occasionally a transverse wall may appear in the stalk cell 

 before the periclinal walls are formed in the antheridial cell (fig. 

 12), but usually the divisions of the stalk cell follow the formation 

 of the primary wall cells. Sometimes, also, the first division of 

 the stalk cell may be transverse instead of vertical (fig. 16). 

 Further development of the spermatogenous tissue is like that of 

 the other Jungermanniaceae anacrogynae. The stalk of the 

 mature antheridium is commonly 4 cells in length, and invariably 

 shows 4 cells in cross-section. The sperms are very small, slender, 

 and extremely coiled before their escape from the antheridium. 

 Each bears a pair of long terminal cilia. The sperms are produced 

 in pairs from the sperm mother cells, but their development is not 

 favorable for critical cytological study because of their extremely 

 small size. 



Archegonium. — The archegonium originates from a papillate 

 initial which may be formed from the first segment of the apical cell 

 (figs. 21-23). This feature brings Fossombronia very close to the 

 acrogynous Jungermanniales. In no case was an archegonium 

 seen arising directly from the apical cell; consequently its activities 

 are not checked by the production of sex organs. 



