48 'Wisconsin Academy of Sciences, Arts, and Letters. 
46. The two nuclear cavities are continuous. 
47. Cytoplasm completely fused. The fusion nucleus kid- 
ney-shaped. 
Plate 4. 
Figures 38-41. Aspidium falcatum. 
38. Median longitudinal section of young apogamous out¬ 
growth. 
39. Older sporophyte showing radial rows of cells. Vascu¬ 
lar tissue present. 
40. Still older. The boundary between gametophytic and 
sporophytic tissues obscure. 
41. Sporophyte has developed the first leaf (1). The first 
root (r) is just breaking through, s is the newly organized 
stem apex. 
Plate 5. 
Aspidium falcatum. 
48. Fusion nucleus kidney shaped. Cytoplasm is not fused 
on the concave side of the nucleus. 
49. Cytoplasm fused. Nucleus still shows its double nature. 
Chromatin threads show pairing. 
50. Furrow remains in the cytoplasm at the plane of fusion. 
Chromatin threads show pairing. 
51. Fusion just completed. 
52. Older. Cell rounded. Occasional paired threads. 
53. Incomplete fusion. Synapsis. A dense tangle of 
threads in each nuclear cavity. Similar threads run from one 
mass to the other. 
54. Early post-synapsis. Nucleus eccentric. The tangle of 
threads is loosening. Threads very long, uniform in diameter 
and can not he seen to be double. 
55. Nucleus central. Slender double threads. 
56. Segmentation. Double chromosomes. Spirem thicker. 
57. Equatorial plate of heterotypic division. 
58. Equatorial plate of homoeotypic division. 
59. Central spindles after the last division. 
