100 HOFMEISTER, ON 



large, central cell, with comparatively small germinal vesicles 

 (PL XIV, figs. 14"' *). 



The base of the young archegonium is surrounded by 

 a small, annular sheath, which, before impregnation, is 

 only from one to four cells in height (PL XIV, fig. 14 b). 

 After the commencement of the formation of the fruit 

 this sheath grows rapidly into a narrow-mouthed, pitcher- 

 shaped covering, consisting of a single layer of cells 

 (PL XIV, figs. 12, 13, 18). 



The impregnated germinal vesicle swells at once to the 

 size of the pear-shaped ventral cavity of the archegonium 

 (PL XIV, fig. 13), and follows the enlargement of that 

 cavity, which enlargement is caused by the active multi- 

 plication of the cells enclosing it. The first division of 

 the primary cell of the fruit takes place by a horizontal 

 septum, which divides the cell into a semi-oval superior, 

 and a filiform inferior, moiety (PL XIV, fig. 15). By 

 repeated transverse division the latter becomes the fruit- 

 stalk, consisting of a single row of cells, the lower end 

 of which, at a later period, and by means of divisions 

 caused by septa parallel to the axis, becomes transformed 

 into a clavate, cellular body (PL XIV, fig. IS). The 

 upper half becomes the capsule of the fruit ; according to 

 the general rule in the Ricciese and Marchantieae, it mul- 

 tiplies by repeated divisions of the cells of the first de- 

 gree by means of septa inclined alternately to the rio-ht 

 and to the left (PL XIV, fig. 15). After about eight 

 such divisions the capsule becomes globular; its outer 

 layer, the cells of which become tabular, forms the wall. 

 The cells of the interior, becoming loosened and spheri- 

 cal in shape, perfect themselves in different ways. The 

 contents of half of them become turbid from numerous 

 fine granules, and their walls increase in thickness. 

 These are mother-cells, containing in their interior four 

 special-mother-cells, usually arranged in a tetrahedron, 

 from which the spores, which are clothed with a strong, 

 delicately marked episporium, are developed (PL XIV, 

 fig. 19). The formation of only two spores in a mother- 

 cell is an irregularity of frequent occurrence. The other 

 cells of the contents of the capsule remain thin-walled, 



