9 
Embryo of Cephalotaxus drupacea. 
Fig. 13 it will be seen that the cells are arranged in rows which converge 
towards the centre of the prothallium. By comparing this with Fig. 11 
one may safely infer that these slanting rows or lines of cells were formed 
from the ingrowing primary cells. 
The Archegonia. 
The first indications of archegonial initials were observed in material 
collected early in April, somewhat over a year from the time the mega- 
sporangium first made its appearance. They are generally but four in 
number and are clearly of superficial origin. In the earliest stages 
observed the initial cells were not much larger than the surrounding 
sterile cells, and only their granular cytoplasm and deeply-staining nuclei 
differentiated them from the latter. At a very early stage the initial 
divides, giving rise to the first neck-cell and the central cell. The primary 
neck-cell almost immediately divides by an anticlinal wall, and thus forms 
the two neck-cells. It frequently happens that one of these divides again 
anticlinally, so that the mature archegonium may present two or three 
cells in the neck in cross-section, as shown in Fig. 15. The neck-cells 
are easily distinguished from the other superficial cells of the prothallium 
by their densely granular contents. Among the Coniferales the number 
of neck-cells to the archegonium seems to vary considerably ; even in the 
same species the number is not at all constant. There are never less than 
two, however, and that seemed to be the prevalent number in Cephalotaxus. 
Fig. 14 shows a longitudinal section of a young archegonium and the 
position of the two neck-cells from this view. 
As soon as the neck-cells became organized, the central cell grows 
very rapidly, and its nucleus, which at this early stage is centrally located, 
increases to fully five or six times its original size. Its cytoplasm also 
becomes much more densely granular and stains more deeply. The 
four archegonia, as may be seen from Figs. 15 and 16, lie close together, 
with but a few layers of small prothallial cells between them, and with 
their necks lying freely exposed, during these early stages, at the more 
or less flat or convex surface of the top of the prothallium. As the 
archegonia continue their development, the upper sterile portion of 
the prothallium grows forward, leaving the archegonia behind. This growth 
progresses until a considerable cavity or archegonial chamber is formed 
immediately over each archegonium, as shown in Figs. 34 and 25. A similar 
depression of the archegonia occurs in Torreya californica (Robertson, 
’ 04 ), also in Taxus (Jager, ’ 99 ). 
At a very early stage in the development of the archegonium (Fig. 14), 
the sterile cells immediately surrounding it become very densely granular 
and very soon acquire the characteristics of the sheath or jacket-cells 
so commonly met with throughout the Conifers. These cells increase 
