17. Bolbitis costata (C. Presl) Ching in C. Christensen, Index Filic., Suppl. 3: 47. 1934.
紫轴实蕨 zi zhou shi jue
Campium costatum C. Presl, Tent. Pterid. 239. 1836.
Rhizome up to 10 cm, up to 15 mm in diam., with 2-4 rows of fronds, covered with lanceolate (ca. 5 × 1 mm), subclathrate, light brown scales. Sterile fronds pinnate, 55-120 cm; stipe 20-60 cm, 2-7 mm in diam. near base, with 5-20 vascular bundles; lamina purplish when dried, 35-75 × 20-40 cm, widest at or below middle, subleathery, terminal segment 20-40 cm, bulbil subterminal on terminal segment or pinnae; rachis not winged; pinnae 3-19 pairs, opposite or alternate, up to 8 cm apart, 16-45 × 4-9 cm, base symmetrical, acute to subcordate, margin entire or crenulate, sometimes crisped, apex rather abruptly narrowing into acute or acuminate tip, lowermost 2 pinnae 1-6 mm stalked; veins for greater part forming 4 or more regular rows of areoles, part of areoles with 1(or 2) included free veinlet, veinlets 5-8 arising from either side of lateral veins. Fertile fronds 40-170 cm; stipe 20-100 cm; lamina 15-85 × 7-30 cm, terminal segment 8-20 cm; pinnae 5-18 pairs, up to 11 cm apart, linear, ca. 22 × 0.6-2 cm, lowermost 2 pinnae 1-6 mm stalked. Sporangia inserted mainly on veins, arrangement usually acrostichoid, rarely gymnogrammoid.
Forests near streams; sea level to 1200 m. Yunnan [Bangladesh, India, Myanmar, Nepal, Thailand].
Bolbitis costata is similar to B. scalpturata in its fronds usually turning purplish when dry; it differs by having broader sterile pinnae (to 4-9 cm), 5-8 veinlets arising from each side of lateral veins, and fertile pinnae linear (14-16 × as long as wide).