Perennial fern ally 3 - 9 cm tall Leaves: of upright stems spreading, stalkless, green, 5 - 6 mm long, 0.5 - 0.8 mm wide, linear to lance-shaped, and usually non-toothed. Spores: hundreds per sac, all of one kind, thick-walled, wrinkled, three-sectioned (trilete) with pointed angles. The spores give rise to the gametophyte (the sexual phase of the plant), which is small, pincushion-shaped, green, photosynthetic, and on substrate surface rather than buried. Upright stems: usually single, but sometimes two from same node, unbranched, green, leafy, and more slender than horizontal stem (4 - 7 mm diameter). Horizontal stem: on top of soil or substrate surface, 3 - 12 cm long, slender (5 - 9 mm diameter; excluding leaves only 0.5 - 0.9 mm), covered with spreading, upcurved, 5 - 6 mm long, 0.5 - 0.7 mm wide, non-toothed, linear leaves, and also with slender roots emerging on underside of stem.
Similar species: Lycopodiella inundata is a bit different from our other species of Lycopodiella since it is so small. The other two species in the Chicago Region, L. margueritae and L. subappressa, are typically at least 9 cm tall, the horizontal stems (excluding leaves) are over 1 mm in diameter, their strobili are usually over 2 cm long, and the sporophylls are appressed. Sterile hybrids between these two species and L. inundata have also been reported in the Chicago Region.
Habitat and ecology: Rare, typically now only in sand pits or other sandy habitats that have been excavated down to the water table in our eastern counties. However, this species could also be expected in bogs, lake shores, and marshes.
Occurence in the Chicago region: native
Notes: This species has the most expansive range of all Lycopodiella in the northern half of North America. It has a disrupted range in the central part of the continent to our west. Species of Lycopodiella hybridize freely, and when the parent species have the same ploidy level the hybrids are fertile. Lycopodiella inundata can hybridize with the other two species of the Chicago Region, L. subappressa and L. margueritae, but since they are of a different ploidy level, the hybrids are sterile. The most common species in the Chicago Region is probably L. margueritae.
Etymology: Lycopodiella is a combination of the genus name Lycopodium, and the suffix ella, referring to the diminutive form (smaller) of this genus compared to Lycopodium. Inundata is Latin for "to cover with water".
Sterile stems ±prostrate, irregularly rooting, flattened, the lvs of the lower side twisted into an ascending position; lvs 8-10-ranked, linear-subulate, mostly entire, 5-7 נ0.5-0.7 mm; fertile stems few, erect, to 1 dm, 1 mm thick; sporophylls ascending or spreading, crowded into a sessile terminal cone 1.5-5 cm נ6-12 mm, all except the lower abruptly expanded near the base and usually with a single pair of sharp teeth near the expansion, otherwise like the lvs; sporangia subglobose, 1-1.3 mm wide; spores 43 microns or more in diameter, the sides convex, the outer face wavy-reticulate, the commissural faces papillose, the commissures sunken in deep furrows; 2n=156. Acid soil of bogs, shores, and meadows, often in seasonally inundated sites; circumboreal, s. to Md., sw. Va., O., Wis., Minn., and Calif.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.