94 HOFMEISTER, ON 



stem as the latter increases upwards in thickness. In this 

 way the outer side of the covering of the antheridium 

 amalgamates with the adjoining cells of the stem. The con- 

 tents of these united cells of the antheridum-sheaths become 

 exactly similar to that of the cells of the upper half of the 

 flat stem ; numerous chlorophyll-granules are formed in 

 them, and air makes its appearance in the adjoining inter- 

 cellular spaces. The rudiment of the antheridium, which 

 as yet consists of few cells, has in the mean time considerably 

 increased in size, and become transformed into an oval, 

 cellular body by means of repeated longitudinal and trans- 

 verse divisions ; this oval body consists of a central group 

 of cells, with turbid, mucilaginous contents, surrounded by 

 a layer of tabular cells with watery contents (PL XII 1, 

 fig. 8). The repeated bisection of the former cells in all 

 three directions leads ultimately to the formation of a 

 spherical mass of numerous, very small, tessellated cells, 

 during the production of which the peripheral layer of 

 tabular cells is gradually entirely displaced (PL XIII, 

 fig. 9). The skin -like membrane of the ripening anthe- 

 ridium becomes closely applied to the inner side of the 

 covering of the antheridium, but without growing to it. 

 Each of the small cells produce, during the progress of 

 growth of the antheridium, a small, lenticular vesicle. When 

 the antheridium is ripe the walls of those small cells swell 

 up into a tough jelly, and the outer membrane of the anthe- 

 ridium assumes a delicate, gelatinous consistence. 



The amalgamation of the cells of the tissue of the stem 

 with the outer side of the antheridium-sheath does not extend 

 to the young, blunt apex of the latter. Owing to the fact 

 that the longitudinal expansion of its cells first takes place 

 after the complete formation of the stern-joints, this free 

 upper end remains for some time in the form of a rounded, 

 little cone, concealed between the epidermal cells (PL XIII, 

 fig. 9). Suddenly the apex elongates itself considerably ; 

 by expansion of its cells it often protrudes more than a line 

 above the surface of the stem. The universal expansion 

 of its cells causes a widening of the mouth of the canal 

 which traverses the axis of the sheath, and which leads to 

 the antheridium (PL XIII, fig. 10). Through this canal 



