Azolla filiculoides , Lam. 187 
Fig. 54. Two transverse sections of a prothallium showing three archegonia. 
x 250. 
Fig. 55. Transverse section of an old prothallium with nine archegonia. 
Figs. 56-59. Development of the archegonium. X350. b, ventral canal-cell; 
c, neck-canal-cell ; 0 , egg. 
Fig. 60. Prothallium showing its relation to the spore, iji , indusium ; sp , re- 
mains of sporangium ; x , upper part of epispore forced aside by the growth of 
the prothallium, x 100. 
Fig. 61. Section of prothallium containing a two-celled embryo, x 350. 
Fig. 62. Vertical section of a three-celled embryo. X350. In this and the 
succeeding Figures, b , indicates the basal wall; II, the quadrant-walls; III, the 
octant-walls. 
Fig. 63. An eight-celled embryo, x 350. 
Fig. 64. Two horizontal sections ( a and b) of a young embryo, x 350. The 
stem st has a two-sided apical cell. L, cotyledon ; st, stem ; f, foot ; r, root. 
Fig. 65. Vertical section of young embryo, with nearly vertical basal wall 
b~b. x 350. 
Fig. 66. Three sections of a young embryo, cut parallel to the quadrant-wall, 
x 35°* x - x', initial cells of cotyledon. 
Fig. 67. Two sections of an embryo of about the same age as in Fig. 66, but 
cut longitudinally. 
Fig. 68. Slightly older stage ; the root has formed the cap-cell. X350. 
Fig. 69. Horizontal section of an older embryo passing through the stem-apex, 
x 350. Z 1 , Z 2 , Z 3 , the three first leaves; x, apical cell of the stem. 
Fig. 70. A similar section of an older embryo, showing the origin of the second 
root, x 350. h, hairs. 
Fig. 71. Two longitudinal sections of an embryo, somewhat younger than the 
one shown in Fig. 64 : x, apical cell of stem ; h, hair ; L' , cotyledon, x 350. 
Fig. 72. a, b, c, d. Transverse sections of an embryo of about the same age. 
X 35 °- 
Fig. 73* Longitudinal section of the first root of an older embryo. X350. 
Fig. 74. Longitudinal section of young plant showing the arrangement of the 
primary fibro-vascular bundles, x 100. 
Fig. 75. Young plant still attached to the macrospore {sp). x 40. r, first 
root. 
v, d, ventral and dorsal cells of a segment cut off from the apical cell of the stem. 
O 
