1904] GARBER: RICCIOCARPUS NATANS 1607 
into an upper cover cell, and a central cell which is to give rise 
to the axial row. This latter division is quickly followed by 
divisions in the outer wall cells, when the archegonium is com- 
posed of two tiers of four cells each. Successive divisions in 
the outer cells lengthen the neck and enlarge the venter. 
The upper of the first two cells of the central row by two 
successive divisions produces regularly four neck canal cells, the 
same number as that reported for the species of Riccia which 
have been studied. The lower of the first two cells enlarges 
very rapidly and shortly before fertilization divides, giving rise 
to a small ventral canal cell and the egg cell (figs. 20-22). The 
egg fills the entire venter of the archegonium, except the small 
portion occupied by the ventral canal cell. Its protoplasm is at 
first somewhat vacuolate, but it rapidly becomes denser by the 
increase of food materials. Starch grains inclosed in plastids 
are so numerous at the time of fertilization as to be conspicuous 
even with moderate magnification. The surface of the egg next 
to the ventral canal cell is concave, and this condition disap- 
pears only with the resorption of the ventral canal cell, when 
the egg assumes a nearly spherical or a somewhat oval shape. 
The breaking down and resorption of the ventral canal cell 
seem to be dependent upon the entrance of the sperm, for the 
degenerate ventral canal cell is still to be recognized in arche- 
gonia that have failed to be fertilized, and in which the egg is 
rapidly shrinking and approaching complete disorganization, as 
in fig. 26. 
The basal cell is larger than the outer one which forms the 
archegonium proper (figs. 72, 13). Two vertical walls very early 
divide it into four cells (figs. z4-16). Later divisions in various 
- directions form a prominent mass of cells imbedded, with the 
exception of the short stalk, in the storage tissue beneath (fig. 39). 
This mass of cells appears to digest the abundant starch of the 
Storage cells, so that it may be readily transferred to the grow: 
ing sporophyte. The appearance and position of this tissue in 
relation to the storage mass indicates that it is the physiological 
equivalent of the foot of the sporophyte in higher forms. 
Campbell (7) states for Riccia in general that the basal cell 
