Lyon: OBSERVATIONS ON EMBRYOGENY OF NELUMBO. 647 
nuclei between which thin cell walls are very early apparent 
(Figs. 1, 4-7). 
Stage B. Monocotyledonous stage.—The spherical embryo 
begins to evidence a maximum growth in the horizontal direc- 
tion, its greater dimension being diagonal or nearly at right 
angles to the longer axis of the ovule. At this time it can per- 
haps best be described as a flattened mass or button of tissue 
lying in the upper end of the ovular cavity. The surface in 
contact with the ovular wall conforms to the shape of the latter. 
The free surface is more or less flattened and slightly inclined 
to the plane of the horizontal. The plumule (a, Fig. 8) now 
arises as a small protuberance on the inclined free surface in a 
median line near its lower side. The axis of the plumule is 
from the first about parallel with the axis of the ovule,-and as 
it grows straight down into the ovular cavity it causes this side 
of the embryo, which we will term the front side, to become 
flattened. The future cotyledon is now evident as a crescent- 
shaped mound of tissue (40, Fig. 8) around the rear of the em- 
bryo, its wings extending forward even with the plumule. This 
' stage culminates in an embryo as represented in Fig. 8. The 
endosperm, during the monocotyledonary stage, forms a co- 
lumnar mass of tissue which stands centrally in the cavity, ex- 
tending from the embryo to the persistent nucellar tissue in the 
lower portion of the ovule. 
Stage C. ‘*Dicotyledonous’’ stage.—The cotyledon be- 
comes bilobed through the localization of growth at the foci, 6 
and 4, Fig. 8. From each of these points a cotyledonary lobe 
grows rapidly downward outside the endosperm, the tissue of 
the nucellus disorganizing before it (Fig. 10). In cross section 
these lobes are crescent-shaped (Fig. 16) and simultaneously 
with their elongation growth takes place in both radial and tan- 
gential directions, each lobe at its base growing forward around 
the plumule. An idea of the relative positions occupied by the 
different structures may be derived from Figs. 13-16; cross 
sections of embryos which were, however, considerably older 
than the one represented in Fig. 9. 
The growth of the plumule is slow during this stage, it being 
a simple dome-shaped mound of tissue (Figs. 9, 10 and 18) 
which comes to occupy a central position through the growing 
forward of the cotyledonary lobes. 
At about this time the plerome first becomes apparent as a 
