r and distribution of spores on the dish. Over the next several laboratory session, it will be your job to carefully observe these spores and what happens to them. When you arrive for your lab period the first thing that you should do is check your fern cultures – it will only take a few minutes! Make good notes and drawings of what you see. You will be given additional instructions and questions to aid in your observations.
Have you observed the fern cultures that you inoculated last week?. By this time many spores should be germinated. Can you see anything without a microscope? Observe the size, color, and distribution of germinated spores through the lid of the dish with the dissecting microscope and compare and contrast the appearance of your spores with the observations you made last week. You can identify the developing ferns because they will always be growing out of spores. What is happening when spores germinate? Have all the spores germinated? What could be the reasons for the germination of some spores and not others? Are there fungal, bacterial or algal contaminants on the plate? Where do these contaminants come from?
Carefully lift the lid of the culture and remove a few of the germinated spores using a probe. Prepare a wet mount of the germinated spores and observe them under the microscope. Locate the original spore walls. What has happened to the spore wall? The minute plants poking out of the spore wall should be green. Locate the rhizoids. What is the function of rhizoids in a plant that is composed of only a few cells? Locate cells that contain chloroplasts. Draw several of these young plants and label the spore wall, rhizoids, and photosynthetic cells with chloroplasts. What differences are there, if any, among the young plants that you observed? Replace your dish into the sandwich bag and put it back in the culture area.
As in the last laboratory, you should start by observing your fern cultures. As before, observe the fern plants on the dish and record your observations. Can you see anything without a microscope? Identify the two morphologically distinct kinds of gametophytes (prothallia, sing. prothallus). The larger mitten-shaped gametophytes produce both male and female sex organs. The male sex organs (antheridia, sing. antheridium) are found around the margins of the plant and near the rhizoids at the lower part of the plant. The female sex organs (archegonia, sing. archegonium) are aggregated near the growing notch, usually on the underside of the plant. Among these larger gametophytes should be numerous small, exclusively male plants. Each male gametophyte consists of numerous antheridia that give a bumpy appearance to the plant. These males develop in response to the presence of a special chemical (antheridiogen) in the medium that is secreted by older gametophytes. Can you think of any ecological or genetic advantages for such a condition in nature?
Make a wet mount that includes a few gametophytes of both types and observe your slide under the compound microscope. Draw one of each type of gametophyte, include and label the spore wall, rhizoids, photosynthetic cells, sex organs, and growing notch. What is different about these two types of gametophytes? How have the gametophytes changed from last week?
In addition, this week you should see the male gametes or spermatozoids in action. Prepare a new wet mount of several of the older male gametophytes so that you can carefully observe their antheridia, include one or two of the larger mitten-shaped gametophytes that have one to three archegonia. Over the next 5 minutes continually observe the antheridia with the compound microscope. What happens to antheridia? What does water do? Where do sperm cells come from? When you see movement, increase the magnification, and observe these small, flagellated gametes. Be very patient – give it some time. The sperm cells can move very quickly and are hard to examine unless they are caught on something or slow down. Draw and describe the shape of the sperm cells and try to locate flagella.
Once you have obse