Cetera 
1901] SPORANGIA AND GAMETOPHYTES OF SELAGINELLA IgI 
archegonia, and a lower vegetative region. The delimitation of the arche- 
gonial region is shown by the trefoil shaped cleft seen in the lowermost spore 
of fig. 58. 
Figs. 54 and 55. Section of female gametophyte showing archegonia, 
Details of the process of division in the unshaded cells of fg. 54 are rep- 
resented in figs. 26-28. 
FIG. 56. Two embryos, one of two cells, the other of three, lying side by 
side in one venter. All walls shown are parallel to the axis of the arche- 
gonium. Compare relative position of these embryos with that of the egg 
and ventral canal cell in figs. 29, 32. 
FiG. 57. Embryo zz situ. The root lies toward the apex of the gamet- 
ophyte. At the right the club-shaped foot of large cells is embedded in the 
prothallial tissue. The embryo is bent with respect to its long axis so that 
the stem apex and cotyledons are brought nearer the root than appears in 
the drawing, which is a reconstruction from serial sections. The two leaves 
with their relatively large ligules are developed successively and envelop the 
tip of the stem (shown by dotted line). The embryo is still within the spore 
wall and sporangium. 
Fig. 58. Vertical section of megasporangium containing three female 
gametophytes. The lowermost shows the trefoil-shaped cleft in the apical 
region of the spore wall, exposing the archegonia. The two other oblique 
sections are not so advanced in development. The pad of tissue at the base 
of the sporangium lies above a region of storage cells in contact with the 
vascular bundles of axis and sporophyte. 
PLATE VIII. Selaginella apus. 
All drawings made with oc. ?, oil immersion, obj. yy, excepting 60-62. 
Figs. 60, 61 were drawn with oc. 2, oil immersion, obj. yy. Fig. 62 with 
oc. 3, obj. 2. 
FIG. 59. Section of microsporangium, showing microspore mother cells, 
goneoes inner and outer layers of sporangium wall. 
G. 60. Median vertical section of microsporangium with mother cells in 
rene stage. Sub-archesporial pad developing at base of sporangi 
Fic. 61. Slightly oblique section of microsporangium showing sic hecoees 
in groups of four (tetrads). 
F1G. 62. Median vertical section of microsporangium to show sporangium 
wall at maturity. Dehiscence region cut across at apex. Sporangium 
Opens in two valves, the subarchesporial pad at top of pedicel serving asa 
fulcrum. 
Figs. 63, 64. Microspore mother cells during first division of nucleus. 
Figs. 65, 66. Sextuple spindle stage with nuclear plates. 
Fig. 67. Exterior view of young microspore. 
