Sex and the Single Cryptogam j 467467 467
instruments on the various stages of cryptogam life cycles, with the result that many new
structures never before seen were discovered. An important advance was made by Johann
Hedwig, a physician who became Professor of Botany and Director of the Botanical Garden
at the University of Leipzig. While studying the germination and growth of moss spores,
Hedwig observed that the first product of germination was a green, algal- like filament,
which today we call the protonema (see Figure 17.1).^11 Soon, tiny buds emerged from the fila-
ment, and these buds grew vertically to form the green, leafy structures we associate with
moss (see Figure 17.1).
Hedwig also identified two types of sexual structures at the tips of some of the leafy
structures (Figure 17.2). One type had bulbous ends, which he assumed were miniature
“stamens.” The other type was vase- shaped with a long neck, which he compared to tiny
“pistils.” Peering through a microscope at the tiny “stamens,” he was able to observe the
release of what he called “corpuscles.” Hedwig hypothesized that these “corpuscles” were
the pollen- like structures that entered the necks of the moss “pistils” and fertilized them.
In today’s terminology, Hedwig’s tiny “stamens” on the tips of male moss branches are
called antheridia (si n g u l a r, antheridium), while the miniature “pistils” on the tips of female
branches are termed archegonia (si n g u l a r, archegonium) (see Figure 7.2).^12 The fertilized egg,Figure 17.2 Stages of sexual reproduction in the life cycle of a moss. A,B. Male and female leafy
structures bear antheridia and archegonia at their tips. C. The motile sperm cells produced by the
antheridia are carried in rain droplets to the neck of the archegonia, where they swim down the
narrow canal and fertilize the egg. D. The resulting zygote develops into a new spore capsule with
stalk and grows out of the archegonium.