Mar., 1923] 
SHOWALTER — RICCARDIA PINGUIS 
165 
Fig. 9. Vertical longitudinal section through the primary segment (6) in process of 
its first division; serial section adjacent to and preceding the one shown in figure 10. 
Greenhouse plant of Florida stock. X 160. 
Fig. 10. Median vertical longitudinal section of apical end of vegetative branch 
showing apical cell ( a ). Greenhouse plant of Florida stock. X 160. 
Fig. 11. Vertical transverse section of apical cell (a, b) in process of division; b 
represents the portion which would have become the segment. Greenhouse plant of 
Florida stock. X 160. 
Figs. 12, 13. Successive vertical longitudinal sections of a young archegonial branch; 
figure 12 shows the apical cell a, figure 13 the secondary segments b' and c and a three-celled 
archegonium ( 9 )• X 230. 
Fig. 14. Longitudinal section of archegonium and two-celled embryo (probably not 
functional); reconstructed from two adjacent sections. X 230. 
Fig. 15. Longitudinal section of archegonium and three-celled embryo; reconstructed 
from four serial sections. X 230. 
Fig. 16. Longitudinal section of nine-celled embryo and gametophyte tissue enlarging 
to form the massive calyptra; V, ventral surface of thallus; D, dorsal surface; reconstructed 
from four serial sections. X 116. 
Fig. 17. Longitudinal section of young calyptra and young sporophyte; V, ventral 
surface of thallus; D, dorsal surface; reconstructed from three serial sections. X 116. 
Fig. 18. Outline of longitudinal section of mature calyptra and nearly mature sporo¬ 
phyte; reconstructed from two sections not adjacent. Greenhouse plant of Wisconsin 
stock grown in 1920. X 20. 
Plate XVII 
Longitudinal sections of archegonia. 
Fig. 19. Very young archegonium showing the mother cell of the axial row. X 950. 
Fig. 20. Mother cell of axial row in early prophase of division. X 950. 
Fig. 21. Mother cell of axial row with division almost completed. X 950. 
Fig. 22. Central cell and neck-canal mother cell formed by first division. X 950. 
Fig. 23. First division of neck-canal mother cell in progress. X 950. 
Fig. 24. Axial row of three penultimate cells, the central cell and two neck-canal cells. 
X 618. 
Fig. 25. Early prophase of division of the central cell. X 618. 
Fig. 26. Late telophase of division of the central cell. X 375. 
Figs. 27, 28. Axial row of four cells—egg, ventral canal cell, and two penultimate 
neck-canal cells. X 375. 
Plate XVIII 
Fig. 29. Lower penultimate neck-canal cell in process of division. X 375. 
Fig. 30. Axial row consisting of five cells—egg, ventral canal cell, two ultimate neck- 
canal cells, and the upper penultimate neck-canal cell, the latter in prophase of division. 
X 375- 
Fig. 31. Mature axial row consisting of egg, ventral canal cell, and two binucleate 
neck-canal cells; reconstructed from three serial sections. X 375. 
Fig. 32. Axial row consisting of egg, ventral canal cell, and one penultimate neck- 
canal cell; reconstructed from two sections. X 375. 
Fig. 33. Mature archegonium with egg ready for fertilization, antherozoid present 
in venter; reconstructed from two sections. X 375. 
Fig. 34. Axial row consisting of egg, ventral canal cell, and three penultimate neck- 
canal cells; reconstructed from four serial sections. X 375. 
Fig. 35. Similar to figure 34, except probably a little older; reconstructed from two 
sections. X 375. 
