Lyon : OBSERVATIONS ON EMBRYOGENY OF NELUMBO. 647 



nuclei between which thin cell walls are very early apparent 

 (Figs, i, 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 (, 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 (bb, 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, b 

 and 3, 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 



