47 8 Yasui . — On the Life-history of Salvinia natans. 
Fertilization. 
When the egg-cell becomes mature, the neck of the archegonium opens 
widely, and the slimy substance, resulting from the disintegration of the canal- 
cell and ventral canal-cell, comes out of the opening (PI. XLIII, Fig. 98). 
The cytoplasm of the egg-cell is often denser around the nucleus, show- 
ing a more or less fibrillar structure. The nucleus contains a large nucleolus 
and a faint, poorly developed reticulum (Fig. 96). 
A great many spermatozoids enter the neck of the archegonium and 
reach the exposed surface of the egg-cell (Fig. 98). Normally only one of 
them penetrates the cytoplasm of the egg. Fig. 97 shows the egg-nucleus 
just after the entering of the sperm-nucleus. The latter appears as a short 
curved rod near the nucleolus of the former. The sperm-nucleus then 
seems to disorganize into amass of granules of various sizes. Fig. 98 shows 
the sperm-nucleus about half-way disintegrated, closely attached to the 
nucleolus. 
Embryo. 
The first division of the fertilized egg was not found. The wall sepa- 
rating the two cells of the embryo is parallel to the axis of the archegonium 
(Figs. 10 1, 102). The next division in each of the two embryonal cells is 
transverse, and thus the quadrants are formed which represent respectively 
the stem, the cotyledon, the foot, and the root (Figs. 103, 105). The cells 
of the cotyledon and the stem quadrants have always denser cytoplasm than 
the other two quadrants. 
The cells of the quadrant both of cotyledon and stem divide by walls 
perpendicular to both of the first two walls (Fig. 104). In the stem-quadrant 
one of the two cells now formed becomes an initial of the apical cell, and it 
divides by a more or less oblique transverse wall, thus cutting off an apical 
cell above. The other cell of the stem-quadrant also divides like its sister- 
cell, and later develops into the first leaf of the young stem. 
The early divisions in the cells of the cotyledonary quadrant do not differ 
much from those of the stem-quadrant mentioned above. But later they 
develop into a quite different structure, and thus, growing rapidly towards 
both sides and below, a triangular cotyledon is formed (Figs. 106-m). 
In the root- and foot-quadrants the cell-divisions are not so regular as 
those of the stem or cotyledon. The development of the root ceases at an 
early stage, and later its tissue cannot be distinguished from that of the foot. 
The foot, on the other hand, develops to a massive structure. The lowest 
cells of the foot are filled with rather dense cytoplasm. 
Pringsheim (’ 63 ) mentions that the triangular shape of the cotyledon is 
due to the presence of the three apical cells at its three corners, but I 
cannot confirm his statement. The cell at each corner of the triangle is not 
