450 SPERMATOPHYTES (SEED PLANTS) 
number, are produced at the micropylar end, and have much 
shorter necks and are simpler in other ways than the archegonia 
of Pteridophytes. The eggs are large and the most conspicuous 
part of the archegonia. A section through an ovule ready for 
fertilization looks like the one shown in Figure 399. 
Male Gametophyte.— The microspores or pollen grains, as they 
may now be called since they have to be transferred to the ovule 
before they can function, usually contain three-celled gameto- 
phytes at the time of their shedding, and in this condition they 
reach the megasporangium, pass through the micropyle, and reach 
the pollen chamber, where they are in contact with the beak of 
the nucellus. In this position the three-celled gametophyte, 
which consists of a vegetative, generative, and tube cell, com- 
pletes its development. The miscrospore develops tubes which 
branch and penetrate the beak of the nucellus in various direc- 
tions, and function as absorptive structures. Finally, the beak 
of the nucellus breaks down and thereby a passage way to 
the archegonia is provided. Meanwhile the generative cell 
enters one of the pollen tubes and passes farther into the pollen 
chamber where it divides, forming a stalk cell and a body cell, 
the latter of which forms the sperms, usually two in number. 
The sperms bear a large number of cilia, and after escaping from 
the pollen tube they swim through the watery solution present 
in the chamber and thereby reach the archegonia and finally the 
eggs. 
Thus, when the male gametophyte is mature, it consists of only 
four cells besides the sperms, and there is no structure formed that 
resembles an antheridium. In addition to the absence of an 
antheridium, it should also be noted that pollination and the 
growth of tubes are other new features which occur in connection 
with the male gametophytes of Cycads. It is obvious that the 
introduction of pollination and the growth of pollen tubes must 
accompany the permanent enclosing of the female gametophyte 
in the megasporangium. 
Seed. — The seed is another new feature of the Cycads. After 
fertilization, a young sporophyte (embryo) is developed and is 
pushed well down into the nutritive tissue of the gametophyte 
by a filament of cells (suspensor). During fertilization and the 
development of the embryo, the ovule continues to grow and 
the integument becomes pulpy, while the outer region of the re- 
