52 
PHARMACEUTICAL BOTANY 
Fertilization. —About a year after pollination the pollen tubes, 
lying within the pollen chamber show signs of renewed .activity. 
The tube nucleus passes to the tip of the tube. The generative-cell 
divides to fotm a body and a stalk-cell which pass into the tube. 
The body-cell later forms two sperm nuclei. While these changes are 
taking place the tube is penetrating the nucellus and growing toward 
the embryo sac with its contained female gametophyte. It finally 
enters it, passing between the neck-cells of the archegonium. The 
tip of the tube then breaks and the entire tube contents is emptied 
into the egg. One of the sperm nuclei fuses with the egg nucleus 
and fertilizes it forming an oospore. 
Seed Formation and Distribution. —The oopsore undergoes re¬ 
peated divisions and forms the embryo or young sporophyte plant 
and a suspensor to which it is attached. The embryo is nourished 
by a portion of the prothallus but the greater part of the prothallus 
forms the endosperm tissue of the seed surrounding the embryo. 
The thin nucellus persists as an endosperm covering. The integu¬ 
ment becomes modified to form the hard protective seed coat. A 
portion of the scale of the cone directly above and adjacent to the 
ovule forms a membranous wing which separates from the scale as 
part of the seed. 
By this time (about two years after pollination) the scales of the 
cone, now quite woody, separate, the seeds are shaken out, and many 
are carried for a considerable distance by winds. 
Germination of the Seed. —Under favorable conditions, the seeds 
absorb water and germinate in the spring following their dispersal. 
The hypocotyl of the embryo appears first, arching upward and 
downward, and, straightening out, draws the green cotyledons with 
it which spread out toward the light, while it grows into the soil to 
form the tap root and in time the remainder of the root system. 
Thus the seedling sporophyte is formed which in time develops into 
the mature White Pine tree. 
