It is surprising how many people are not aware, even today, that plants reproduce bisexually in
many species. In
fact the plants have been at it a long time. Algae first began to reproduce bisexually around
1,000,000,000 years
ago. Considering that man has been copulating for a million years or so, the various species of
algae score high
on persistence. A freshwater algae (Ulothrix) is often used to illustrate the origin of gametes,
i.e. the origin of
sex cells. The elongated filament-body of the algae generates a number of small spores which
have lost the
capacity to germinate (as they do in asexual reproduction): the spores come together and fuse
to form a new
individual - one of the simplest instances of the sex act.