Water ferns in petri dishes

Background:

Your fern gametopytes should now look like this (at least under a microscope). They have a heart shape, and though difficult to see, should have mature antheridia with sperm and archegonia with eggs. We will add water to their dishes to allow sperm to reach eggs and fertilization to occur. If this works, we should get formation of zygotes and the start of the dominant, diploid sporophyte generation.

(Instructors: Insert photos of fern gametophyte with antheridia and archegonia labelled here)

Supplies:

Water (bottled water is better than tap water, but tap water can be used)

Disposable pipettor (provided to you by instructor)

Instructions

Your fern gametophytes should have continued to grow since we last looked at them. At this point, they should have archegonia with eggs and antheridia with sperm. We need to create moist conditions for the sperm to swim to the eggs, so fertilization can occur. To accomplish this, you should do the following:

1. open your fern dish, add a few drops of water, only about 1 millimeter deep, and immediately close the dish.

2. Leave the dish for several minutes to half an hour. Then remove the lid, tip the dish to dump out excess water, and immediately re-close the dish.

3. To re-seal the dish, re-wrap it with the parafilm wax that had sealed it, wrap it in plastic wrap, or put it into a plastic ziploc style bag.

A video of fern sperm swimming is linked here; likely better ones from other sources.