1904] WYLIE: ELODEA CANADENSIS 21 
Fig. 34. Embryo sac just before fertilization. The polars lie in contact. 
Fic. 35. Embryo sac at time of fertilization. One sperm lies in contact 
with the endosperm nucleus; the other is uniting with the egg. 
Fic. 36. A similar stage. The pollen tube contents have apparently 
burst out of the synergid. 
Fic. 37. Antipodal group showing five nuclei. 
Fic. 38. Antipodal group. The enlarged nucleus surrounded by dense 
cytoplasm which is bounded by a membrane. 
FIG. 39. An antipodal group similar to 7g. ?§ without membrane about 
enlarged cell. 
Fic. 40. An antipodal group showing three nuclei. 
Fics. 41, 42. Polars as they lie in contact before fertilization. 
PLATE Ill, 
F1G. 43. Cross-section of stamen showing the archesporia of the two 
sporangia. 
Fic. 44. Archesporium cutting off primary wall layer which nearly 
invests the primary sporoyenous cells. 
Fic. 45. Showing several wall layers and cells cut off the sporogenous 
tissue on the axial side of the sporangium. 
1G. 46. Cross-section of stamen after spore mother-cells are established. 
Fic. 47. Spore mother-cell immediately before division. 
Fic. 48. First division of spore mother-cell. 
F1G. 49. Division of daughter-cells. 
Fic. 50. Young tetrad enclosed by wall of mother-cell. 
Fic. 51. Young tetrad free from wall of mother-cell. 
Fic. 52. Division of microspore nucleus. 
Fic. 53. Four spores of tetrad clinging together with their nuclei dividing 
simultaneously. 
Fic. 54. Generative cell being cut off along wall of spore. The tube 
nucleus already enlarged. 
Fic. 55. Generative cell has passed into the cytoplasm of the tube cell. 
Fic. 56. Tube nucleus amoeboid in form, generative cell elongated. 
Fic. 57. Generative cell as it appears before division into the male 
cells. 
Fics. 58-62. Stages in the division of generative cell. 
Fics. 63-66. Male cells joined in pairs by their elongated ends. 
Fic. 67. The spore coats; the exine with spines. 
Fig. 68. A pollen grain at time of pollination, showing tube nucleus and 
male cells. 
Fic. 69. Pollen grain germinating on the stigma of a pistillate flower. 
PLATR IV, 
Figs. 70-74. Cyst-like enlargements formed at ends of pollen tubes in 
ovarian cavity, showing male structures are still distinct cells. 
