188 BOTANICAL GAZETTE | SEPTEMBER 
eventually forms the initial sporangium wall. The hypodermal cell is the 
initial sporogenous cell. The first cell of the ligule is distinguished by a 
black nucleolus. 
Figs. 3 and 4. Radial section of portion of strobilus showing two super- 
ficial archesporial cells (shaded). 
Fic. 5. Radial section of strobilus showing three-celled sporophyll (near 
apex), a two-celled sporangium (shaded) near the base of the subtending 
sporophyll, and the early stage of the vascular system. 
Fic. 6. Radial section of strobilus showing four-celled sporangium pos- 
sibly formed by two archesporial cells which divided by transverse walls. A 
stage subsequent to figs. 3? and ¢ 
Fic. 7. Radial section of older sporangium. Sporogenous cells are 
shaded, and are represented with black nucleoli. 
Fic. 8. Vertical section of sporangium showing definite radial arrange- 
ment of cells and plane of cleavage dividing it into two groups of cells, each 
the progeny of one of the two superficial archesporial cells shown in /g5. 3 
and 4. 
Fic. 9. Vertical median section of sporangium more advanced. Sporan- 
gium wall at this stage consists of one layer. 
Fic. 10. Median transverse section of sporangium showing the sporan- 
gium cells, the tapetum, the inner and the outer layers of the sporangium 
sie 
. Section of sporangium after the spore mother cells are estab- 
ites ue this stage the sporogenous cells are distinguished by two con- 
spicuous masses of granular matter which lie against the nucleus 
iG. 12. Group of sporogenous cells in synapsis stage. Probably micro- 
spore mother cells. 
. 13. Detail of small portion of megasporangium showing megaspore 
ie cell (distinguished by the lumps of matter on either side of the 
nucleus) lying near the glandular tapetal cells. Two sterile sporogenous colt 
are at the left and below the megaspore mother cell. 
Fics. 14-24. Stages in the development of the megaspores. Fig. 16 
shows the characteristic sextuple spindle stage previous to the separation into 
spores, as seen in fig. 78. The four nuclei pass from the bases to the apices 
of the newly formed spores, as shown in figs. 18-22 
Figs. 25-28. Details of cell division in the final ‘ages of development of 
the female prothallium. Fig. 25 represents a portion of a section of the 
stage represented in fg. 49 to show thickness of protoplasmic vesicle and the 
invasion of fibrillae blocking off the separate nuclei. 
FIG. 29. Section of archegonium. The egg and ventral canal cell are 
lying in a plane perpendicular to the long axis of the archegonium. The egg 
is the larger cell with black nucleus. 
