8. Asplenium trichomanes L. ssp. trichomanes (maidenhair
spleenwort) Pl. 2i,j; Map 8
Leaves 3–20 cm long, monomorphic. Petioles reddish brown to nearly black their
entire length, shiny, the color extending to nearly the tip of the rachis. Leaf
blades pinnately compound, linear in outline. Pinnae mostly opposite to
subopposite on the rachis, 2.5–8.0 mm long, the median pinnae 4–7 mm long,
oblong to ovate or wedge-shaped, the margins toothed or shallowly lobed, not
auriculate, the base truncate to wedge-shaped, not overlapping the rachis.
Veins not anastomosing. Spores 64 per sporangium. 2n=72. July–September.
Scattered through the Ozark and Ozark Border Divisions, locally north to
Lincoln County ( U.S., Canada, Europe, Asia, Africa, Australia). Shaded
crevices and ledges of sandstone, chert, or granite bluffs and boulders; rarely
on cherty dolomite bluffs.
Subspecies trichomanes is a widespread, diploid cytotype that usually
occurs on noncalcareous substrates. Its spores are 27–32 mm long. Plants of the
tetraploid ssp. quadrivalens D.E. Mey. occur on calcareous substrates in
North America and have spores that are 37–43 mm long (Moran, 1982). It has been collected in
southwestern Illinois on bluffs immediately across the Mississippi River
floodplain from Missouri. This cytotype should be searched for on shaded
dolomite bluffs in the eastern Ozarks.
No sterile hybrids involving the maidenhair spleenwort have been recorded from
Missouri to date. However, elsewhere this species has been documented to
hybridize with A. pinnatifidum (A. ¥herb-wagneri W.C. Taylor & Mohlenbr.), A.
platyneuron (A. ¥virginicum Maxon), A. rhizophyllum (A. ¥shawneense (R.C. Moran) H.E.
Ballard), and A. ruta-muraria (A. ¥clermontae Syme).