554 LIFE-HISTORIES 
(or embryo-sac) has been developing some very simple archegonia. 
(a), consisting only of a large egg-cell (0), and one or more very 
small cells (c) representing the neck. See also Fig. 379, A. Presently 
the tip of a pollen-tube bearing the male nucleus reaches the egg- 
cell and discharges its nucleus into the female protoplast (Fig. 379 B). 
The male and the female nucleus fuse into one (C) and move to 
the opposite end of the egg-cell, there to form a group of small cells 
from which one or more embryos arise, but only one develops, in 
each seed. As in Selaginella, certain cells form a suspensor which 
pushes the developing embryo into the storage tissue of the game- 
tophyte. But in the pine and spruce this vegetative part of the 
nurse-plant, because of its long connection with the parent, is able 
to draw into itself a continued supply of nutritive material. Part 
of this nourishes the embryo till it develops root, stem, and leaves, 
while a surplus is stored around it as seed-food for the use of the 
plantlet when it has left the parent, and is ready to germinate 
(Figs. 379, 380). Not only is abundant food thus supplied to and 
for the embryo, but the sporangium wall (nucellus and integument) 
and the sac-leaf (cone-scale or carpel) are so well nourished after 
fertilization has taken place, that they grow enormously and be- 
come much hardened as organs of protection. The ripened ovule 
thus becomes a seed, and finally, as already described, separates 
from the parent and is aided in its aerial voyage to a home for life, 
by a wing derived from the carpel. The young sporophyte has 
simply to grow after the manner of its kind to become a tree and 
produce gametophytes which shall codperate in the formation of 
highly favored offspring. 
In view of the many resemblances between Pinaceze and 
Lycopodiacee it has been thought that plants closely related 
to the club-moss trees of the coal-period may have been the 
ancestors of both of these cone bearing groups. It should 
be said, however, that the remains of extinct gymnosperms 
represented by Cordaites (Fig. 277, 5) contemporaneous with 
Lepidodendron, show resemblances to the ancient ferns 
which indicate that the ancestor of the conifers was more 
fern-like than might appear merely from a comparison of 
modern types. | 
Cycas (Fig. 381) shows even closer affinity with ferns, as for in- 
stance, in the ample branched foliage-leaves which unroll as they 
develop, and the numerous sporangia borne upon a sac-leaf. In 
general the life-history is similar to that of Pinus, pollen spores 
being carried by the wind to a little chamber at the tip of a naked 
ovule to fertilize an egg-cell; but in this case the microspore upon 
germinating produces in the pollen-tube two motile gametes pro- 
