After the true ferns, the second most abundant group of spore-producing vascular plants that occur in Denali National Park are the "club mosses", although this name is something of a misnomer because this group of plants in unrelated to the true mosses. Club mosses (or in botanical Latin Lycopodiaceae) superficially resemble mosses, but grow much larger because, unlike mosses, they have highly differentiated and specialized vascular tissue to conduct water and solutes from the soil to above ground tissues. There are eight species of club moss that occur in the park. They are found in all but the most wet or most dry environments. Club mosses occur in habitats spanning from very shady birch forests and alder thickets to open tundra on mountain ridges. In the tundra club mosses tend to occur in snow beds, which is the name for depressions, gullies and other areas where snow accumulates more deeply during the winter and thus remains later in the season than in the surrounding terrain. In snow bed sites club mosses are frequently associated with members of the Heath family such as Cassiope tetragona and C. stelleriana and the grass Hierochloe alpina.