Plants of the Clubmoss Family
The northern hemisphere was covered with vast, swampy forests from about 200 to 250 million years ago. These forests included now-extinct species of the Clubmoss family that grew to more than one hundred feet high! Note that peat moss (Sphagnum) is not a Clubmoss since it has no vascular system.
Clubmosses have horizontal branching stems, either above or below ground. These send up erect shoots ranging in size from a half inch to over a foot tall in some species. Clubmosses produce spores in a cone-like structure at the end of a stalk. They are "homosporous," meaning they produce spores that are neither male nor female. The spores are shed, then germinate to become a minute "thallus," meaning a plant part that is not differentiated into leaves or a stem. The thallus produces male sperm cells and female egg cells. Upon fertilization, the egg cells develop into new plants. The reproductive cycle is exceedingly slow in the club mosses. Twenty years or more can pass between the dropping of the spores and the final germination of the new plant.
Worldwide, there are about 13 genera and 400 species, most of which were formely lumped together within Lycopodium. Due to segregation, there are potentially 7 genera in North America, including Diphasiastrum, Lycopodiella, Palhinhaea, Pseudolycopodiella, Huperzia, and Phlegmariurus. Some taxonomists propose segregating the latter two genera into a new family, Huperziaceae.
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