无盖粉背蕨 wu gai fen bei jue

Allosorus dealbatus C. Presl, Tent. Pterid. 153. 1836, based on Cheilanthes dealbata D. Don, Prodr. Fl. Nepal. 16. 1825, not Pursh (1813); Aleuritopteris doniana S. K. Wu, nom. illeg. superfl.; A. interrupta Saiki; A. sikkimensis S. R. Ghosh; C. doniana Fraser-Jenkins & Khullar.

Rhizomes erect, short; scales bicolorous, black with pale margins, lanceolate. Fronds clustered. Stipe dark brown to black, (15-)20-35 cm × 1.5-2 mm, sparsely scaly at base; scales lanceolate, those at stipe base bicolorous, dark brown with lighter margins, often grading to concolorous above. Lamina lanceolate to somewhat oblong-lanceolate, 20-40 × 7-16 cm, pinnate-bipinnatifid, papery or thinly leathery when dry, abaxially with white farina, adaxially glabrous, apex acuminate; rachis and costae same color as stipe; pinnae 5-20 pairs, sessile, distinct along rachis, basal pair of pinnae largest, inequilateral, triangular-lanceolate, bipinnatifid; pinnules ca. 10 pairs, acroscopic ones smaller, basal basiscopic pinnules largest, 3-4 cm × 1-1.5 mm, pinnatifid; second and third pairs of pinnae of same shape as basal one, but slightly shorter; fourth and upper pairs of pinnae lanceolate. Sori consisting of several sporangia, confluent at maturity. False indusia poorly developed, very narrow, indistinct.

On rocks; 600-1500 m. Guizhou (Xingyi), Yunnan [Bhutan, India, Nepal, Thailand].

This beautiful species is distinguished from its relatives by its large fronds and poorly developed false indusia. Fée listed Aleuritopteris dealbata and A. farinosa (Forsskål) Fée as distinct taxa in his diagnosis of his new genus Aleuritopteris on p. 153. One must presume therefore that when he cited Cheilanthes farinosa Hooker & Greville (Icon. Filic. 2: t. 134. 1831) as a synonym of his A. dealbata, he implicitly restricted their account to the Nepalese element. This was first invalidly described by D. Don and validated by C. Presl, who included Hooker and Greville’s account within his concept of the taxon. Fée’s name was incorrectly treated as invalid by recent Asian authors, but their replacement name, A. doniana, must be treated as a superfluous illegitimate name.