— 67 — 
6, b & c. An average shape of thallus, shows position of 
antheridia and involucre. 
Fig. 7. a & b. Plants collected April 15. 
c. Calyptra. 
Capsule has been pushed through this by the lengthening of 
seta and is just ready to open and shed the spores. 
Thallus ihuch dried down and reduced in size. 
Figs. 1 — 7. All nat. size. 
Fig, 8. Vertical section through thallus X 80, collected July 10. 
e, epidermal cells. p, parenchyma cells, r, rhizoids. 5/^ 
thick. 
Fig. 9. Young sporogonium, Aug, 17, X 20, capsule plainly differen- 
tiated, seta hardly at all. n, withered neck of arche- 
gonium. 
EXPLANATION OF PLATE IX 
DEVELOPMENT OF ANTHERIDIA 
All median longitudinal sections and X 233. 
Fig. 10. Earliest stage, single superficial cell. May 29 (4/^). 
Fig. 10, a. Same stage as 10, Apr. 21 (4/^). 
Fig. 11. Two-celled stage, stalk cell and antheridium mother cell, 
Apr. 21 (4/^). 
Fig. 12. First division of the antheridium mother cell by vertical 
wall, Apr, 21 (4/^). 
Fig. 13. More mature stage. May 29. Shows characteristic shape 
of stalked antheridium enclosed in protecting cavity. Central 
cells by division will form sperm cells surrounded by layer of 
sterile cells (5/^), 
Fig. 14. Somewhat more advanced stage than fig. 13, Apr.* 21 (4/^). 
Fig. 15. Mature antheridium. Apr. 21 (4/a). 
DEVELOPMENT OF ARCH EGON I A 
All X 233. 
Fig. 16. Two early stages of archegonia from Fig. 26, June 14, 
median long, section. 
16a. Single superficial cell ; one celled stage. 
16b. Two-celled stage, archegonium mother cell ready to 
divide into two. 
Fig. 17. Two-celled stage, July 10, median long, section. 
Fig. 18. First division of archegonium mother cell, June 14, median 
long, section. 
Figs, 19 & 20. June 14. 
Shows central cell set off from peripheral cells, optical section. 
Figs. 21. 22, 23. Median longitudinal sections of more advanced 
stages, July 10. 
