1 86 Campbell.- — On the Development of 
Fig. 22. Longitudinal section of young microsporangial sorus. x ioo. col. 
columella. 
Fig. 23. Young microsporangium, x 350. 
Fig. 24. Cross-section of a nearly ripe microsporangium, cutting through two 
massulae. The forming glochidia lie in the space between : n, tapetal nuclei, x 2 50. 
Fig. 25. Ripe microspore ; a , in section ; b, from above. 
PLATE VIII. 
Fig. 26. Nearly ripe microsporangium. X250. 
Fig. 27. A single free massula. x 250. sp, spores; gl, glochidia. 
Fig. 28. Section through a massula containing the prothallia. X350. 
Figs. 29-33. Development of the male prothallium, x 560. /, first wall 
b, basal cell of antheridium ; 0, opercular-cell. 
Fig. 34. Transverse section of a ripe antheridium. x 75 °- a ) a top view; 
b, median section. 
Fig. 35. Median longitudinal section of a ripe macrosporangial sorus. x 100. 
sp, sporangium * wall ; n, Anabaena- cells; z, episporic appendages; ex, part of 
the exospore that has become detached ; ep, lower epispore : id, indusium. 
Fig. 36. Median section through the episporic bodies at the top of the spore, 
x 350. x , one of the three pear-shaped bodies of the so-called ‘ Schwimm- 
apparat ’ ; n, tapetal nuclei. The remains of the sporangium-wall is seen above, 
with Anabaena- cells l>ing over it. 
Fig. 37. Section, parallel to the surface of the spore, of the lower epispore. 
x 350- 
Fig. 38. Median longitudinal section through the base of the sporocarp. x~350. 
ep, epispore ; ex, exospore ; sp, sporangium-wall. 
Fig. 39. Transverse section of the episporic appendages at the top of the spore, 
x 100. 
Fig. 40. Longitudinal section through the upper part of the ungerminated 
macrospore, x 600. ex, exospore ; n, nucleus. 
Fig. 41. Transverse section through the macrospore at the beginning of ger- 
mination. x6oo. nn, nucleolus. 
Fig. 42. First division in the germinating macrospore. x 350. pr, pro- 
thallium-mother-cell. 
Figs. 43-49. Development of the female prothallium, seen in vertical action. 
X 350. Figs. 44 and 46 are diagrams of 43 and 45. b, the basal wall. The 
others are numbered, ar, archegonium. Irt Fig. 48 a, b, and c are consecutive 
sections of the same prothallium. 
PLATE IX. 
Fig. 50. Young prothallium breaking through the epispore. x 250. 
Fig. 51. Full-grown prothallium in vertical section. X350. The archegonium 
has not been fertilized. 
Figs. 52, 53. Two transverse sections of a young prothallium. X350. 0, 
archegonium ; en , endosperm. 
