Eaton's spike-moss

Diplostachyum eatonii (Hieronymus ex Small) Small

Plants terrestrial, forming tiny (1--4 cm), dense clumps. Stems short-creeping, unbranched or few-forked, flat, not articulate, glabrous. Rhizophores axillary, 0.02--0.04 mm diam. Leaves delicate, papery. Lateral leaves spreading, well spaced or crowded toward stem tip, green, ovate to ovate-oblong, 1--1.5 X 0.5--0.9 mm; base rounded; margins transparent, serrate; apex acute. Median leaves lanceolate, 0.8--1.2 X 0.3--0.35 mm; base oblique; margins transparent, serrate; apex bristled; bristle to 1/3 length of leaf. Strobili solitary, 2--3 mm; sporophylls ovate-lanceolate, strongly keeled toward tip, keel dentate, base glabrous, margins serrate, apex long-acuminate.

Hammocks and sink holes in limestone soil; of conservation concern; 0 m; Fla.; West Indies in the Bahamas.

Selaginella eatonii is a minute species, easy to distinguish by its long-bristled leaf apex, iridescent leaf surface, and somewhat transparent sporophylls on the underside of the stem. It does not have any close relatives among the species in the flora. Selaginella eatonii may best be placed within subg. Heterostachys , with which it shares flattened strobili, keeled sporophylls, and a partial laminar flap on the sporophylls. Selaginella eatonii does not have strongly dimorphic sporophylls or a very well-defined laminar flap, and therefore I prefer to treat it here with the other heterophyllous species of subg. Stachygynandrum until a detailed study of subg. Heterostachys can be made.