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.