Reproductive Structures in the Podocarpineae . 59 
The megaspore mother-cell is distinguished early by its rapid increase 
in size and by its large nucleus. It gives rise to a linear tetrad of spores, 
of which the one nearest the base germinates (PL VIII, Fig. 39). Two spores 
occasionally develop into gametophytes. Spongy tissue seems to be entirely 
absent (PI. VI, Fig. 17 and PL VIII, Fig. 39), for the cells immediately 
surrounding the spores and the young sac possess no dense protoplasmic 
contents and are not distinguishable in any way from the other tissue of 
the nucellus. Except for this absence of spongy tissue the young gameto- 
phyte conforms to the usual coniferous type. 
The next stages obtainable, shortly after the endosperm had completed 
its centripetal growth, showed it to be composed of uninucleate cells and 
surrounded by a strongly developed megaspore membrane. The embryo- 
sac of P. spicatus is approximately spherical in shape and about half as large 
as that of P. ferrugineus , which is slightly obovate and nearly twice as long 
as broad. 
The archegonia appear early, while the sac is less than half its final 
size, and are usually two in number, though three sometimes occur. Each 
archegonium arises from a superficial cell, which divides into neck-cell and 
central cell. The latter becomes greatly elongated and the mature arche- 
gonia are often 2 mm. in length, perhaps the largest among vascular plants. 
The nucleus remains near the neck and the contents of the central cell are 
thin, vacuolate and without asteroids. A single layer of jacket cells becomes 
sharply differentiated, and its members, uninucleate at first, soon contain several 
nuclei. The primary neck-cell divides anticlinally into a rosette of from eight 
to twelve cells, and this single tier is the final condition of the neck. 
Meanwhile the endosperm has increased greatly in size and at the apex 
has grown up around the necks of the archegonia and enclosed the ends 
of the waiting pollen-tubes and the male cells which are destined to effect 
fertilization (PL V, Fig. 2 and PL VIII, Fig. 40). Any archegonium towards 
the neck of which no pollen-tube has by this time approached is now 
entirely sealed over by the sterile gametophytic tissue and prevented from 
being fertilized. A cone-shaped region below the archegonia, especially 
long and narrow in P . ferrugineus , is early differentiated as in the other 
species by its smaller and more rectangular cells and by the many nuclei 
which they contain. The remaining cells of the embryo-sac become multi- 
nucleate before fertilization, and the number of nuclei in each cell seems to 
be considerably greater than in the other two sub-genera. 
As the central cell approaches maturity its nucleus divides into egg and 
ventral canal nuclei (Figs. 2 and 41). The latter may immediately go to 
pieces or may persist for some time, and in rare cases increase considerably 
in size. The egg nucleus sinks but slightly below the neck, always remain- 
ing in the upper quarter of the archegonium, and now grows very large 
(Figs. 2 and 40). It has loosely granular contents and is usually surrounded 
