SPERMATOPH YTES 2 1 1 
ing), a generative cell, and a tube nucleus. This is the shedding stage, 
and the subsequent development occurs in the pollen chamber, aftei 
the pollen tube has begun to develop. In that position the nucleus 
of the generative cell divide?, but no wall is formed, the stalk nucleus 
being thrust out to one side of the general cytoplasm, which organizes 
the body cell in connection with the other nucleus. The events that 
follow are exactly as in the cycads: two blepharoplasts appearing in 
the body cell ; the body cell dividing into two sperm mother cells, each 
FIG. 471. Micropylar end of female gametophyte of Ginkgo, showing the endosperm 
beak developed in the archegonial chamber, and the two archegonia; in the left arche- 
gonium the sperm and egg nuclei are fusing; in the right archegonium the early free 
nuclear division of the embryo is occurring. 
with one blepharoplast ; and each mother cell developing a spirally 
grooved, multiciliate sperm, which later is discharged. 
Fertilization. The details of fertilization also resemble those in the 
cycads. The pollen tube is a branching and absorptive (haustorial) 
organ; the pollen chamber and archegonial chamber become continuous 
by the breaking down of the small amount of intervening tissue; the 
grain end of the tube is thus brought into position favorable for the 
discharge of sperms into the archegonial chamber ; and fertilization is 
accomplished (fig. 471). 
Embryo. The embryo is peculiar among gymnosperms in the 
absence of a slender, elongated, and tortuous suspensor, but a real sus- 
pensor is present. Free nuclear division (fig. 471) results in the dis- 
tribution of 256 nuclei through the cytoplasm of the egg, and then walls 
