2. Huperzia porophila (J.N. Lloyd & Underw.) Holub (rock clubmoss) Pl. 18f,g; Map 38

Lycopodium porophilum J.N. Lloyd & Underw.

L. selago L. var. patens (P. Beauv.) Desv.

Stems 7–25 cm long , short-decumbent to strongly ascending. Leaves 6–11 mm long, monomorphic or those with sporangia slightly shorter than the others, linear to narrowly lanceolate, widest near the base, usually entire at the tip, spreading to reflexed, olive green to green, shiny. Stomates present on both leaf surfaces. Gemmae 4–5 mm long, obovate, flattened, the 2 lateral leaves acute and sharply pointed at the tips. 2n=134. June–October.

Uncommon in eastern Missouri (Pennsylvania discontinuously to Minnesota, south to Alabama). Ledges and crevices of shaded sandstone bluffs.

The range of this species is almost entirely contained within that of the more widespread H. lucidula. Where the two species grow together, sterile hybrids commonly occur. These resemble robust plants of H. lucidula, but have abortive spores and only scattered stomates along the outer edges of the upper leaf surfaces. These hybrids have been named H. ¥bartleyi (Cusick) Kartesz & Gandhi. Hybrid plants have been documented from Jefferson, Madison, Ste. Genevieve, and Warren Counties.