Lycophytes: Ancient Vascular Plants
Lycophytes represent one of the oldest lineages of vascular plants on Earth. With about 1,200 species including club mosses, spike mosses, and quillworts, these plants are characterized by their small microphyll leaves—a key feature that distinguishes them from ferns.
Club mosses might look like oversized moss plants, but they're actually vascular plants with true roots, rhizomes, and small scale-like leaves. Their spore-producing structures form either in cone-like strobili at the tips of stems or along the stems. Despite their small size today, some ancient lycophytes grew as large trees!
Spike mosses (genus Selaginella) grow primarily in shady, moist tropical and subtropical environments. They have creeping rhizomes that typically branch in two directions (dichotomously) and overlapping scale-like leaves with a small outgrowth called a ligule. Unlike many other spore-bearing plants, spike mosses produce two different spore types: microspores that develop into male gametophytes and megaspores that develop into female gametophytes.
Cool fact: Quillworts look nothing like typical plants—they have quill-like leaves growing from a swollen underground stem called a corm, and most live in freshwater habitats where they can be completely submerged.
Both spike mosses and quillworts are heterosporous, meaning they produce two kinds of spores—a more advanced reproductive strategy that represents an evolutionary step toward seed plants.