171. Polystichum minutissimum Li Bing Zhang & H. He, Bot. Stud. (Taipei). 50: 353. 2009.
微小耳蕨 wei xiao er jue
Plants evergreen. Rhizome erect, 0.3-0.5 cm, sparsely covered with scales; scales brown, lanceolate, ca. 1.4 mm; roots 1-1.5 cm, ca. 0.23 mm in diam. Fronds 6-9 per rhizome, 1.6-4.1 cm; stipe green, 3.4-8 mm, 0.23-0.45 mm in diam. at middle; basal stipe scales brown, dull, lanceolate, 1-1.5 × 0.35-0.55 mm, papery, margins slightly ciliate, apices acuminate to caudate; distal stipe scales similar but narrower and shorter toward apex of rachis, varying in size, brown, dull, narrowly lanceolate to subulate, papery, margins sparsely shortly ciliate, apices caudate. Lamina 1-pinnate, broadly lanceolate, 1.3-3.8 × 0.7-1.1 cm at middle, contracted toward base, apex obtuse; rachis 0.23-0.45 mm in diam. at middle, without proliferous bulbils; scales of rachis brown, dull, subulate to linear, 0.7-1.2 mm, varying in size, papery, margins ciliate, apices caudate. Pinnae 5-8 pairs, 2 basal pairs 2.3-4.8 mm apart, alternate, attached at ca. 70° angles to rachis, middle pinnae 2.9-5.8 × 2.8-4.5 mm, nearly rectangular, shortly stalked, acroscopic base auriculate, bases cuneate, margins bluntly toothed, apices obtuse; abaxially scaly, adaxially glabrous; microscales on abaxial surface linear, 1.1-2.9 mm; frond texture thinly papery; venation pinnate; midrib slightly raised abaxially, flat adaxially; lateral veins free, 2 or 3 pairs from midrib per pinna, slightly raised and nearly indistinct abaxially, indistinct adaxially. Sori terminal on veins of upper pinnae, 1-3(or 4) per fertile pinna, close to and ca. 0.7 mm distant from margin of pinna; indusia yellowish brown, ca. 0.7 mm in diam., erose.
● Inside karst caves; ca. 800 m. S Guizhou (Libo).
Polystichum minutissimum is similar in stature to P. liboense, which is also found in limestone areas of Libo Xian, Guizhou, but P. liboense is larger with lamina 6.5-10 × 1.2-1.6 cm and the middle pinnae ca. 9 × 4 mm. Most importantly, P. liboense has hydathodes near the margin of the pinnae, while P. minutissimum does not. Both species have nearly rectangular pinnae without spinules on margin.