Psilophyta. The Psilotaceae are leafless and rootless terrestrial or epiphytic homosporous, protostelic vascular plants comprising 2 genera and less than ten species. The free-living sporophytic plant body is a dichotomously branching stem consisting of a subterranean mycorrhizal rhizome and a green, photosynthetic aerial portion that bears very small nonvascularized scale-like flaps of tissue called enations and 2- 3-lobed eusporangia or synangia on very short lateral branches. The independent gametophytes are bisexual, subterranean, lack chlorophyll, and depend on a symbiotic fungus for survival. Biflagellated sperm produced in an antheridium must travel through a film of water to reach the egg of an archegonium in order to initiate the zygote that may develop into a new sporophyte individual.
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Psilotum nudum, moa or whisk fern. This is one of two species of the genus that are native to the Hawaiian Islands. Note the dichotomously branching stem, minute enations, and lateral synangia which release hundreds of white spores. The Hawaiians collected large quantities of these spores and used them like talcum powder. Note that each synangium consists of 3 fused eusporangia on a very short lateral branch. |
