Rhizome slender, 2–4 mm diam., covered with shiny bronze-coloured hairs. Fronds distant, erect, stiff and harsh, 50–130 cm long. Stipe long, 2–4 mm diam., green-brown to straw-coloured, smooth and slightly shiny. Lamina 3-to almost 4-pinnate, more or less triangular, dark green, paler below; hairs on both surfaces scattered, short, pale, non-glandular, bristle-like. Rachises straw-coloured; hairs on both surfaces like those on lamina, the underside also with some coarser, longer hairs with orange-brown cross-walls, shedding to leave small brown tubercles. Pinnules oblong; bases decurrent; margins shallowly serrate, crenate or entire (larger pinnules deeply lobed); apices obtuse or acute; veins conspicuous, close together. Sori away from margin, in 2 rows on pinnule, unprotected; numerous fine hairs projecting from sorus (especially noticeable in immature sori).
GleP, VVP, VRiv, GipP, OtP, WaP, CVU, NIS, EGL, EGU, WPro, HSF, HNF, Strz, MonT, HFE, VAlp. Also Qld, NSW, Tas. (including King Is. and Flinders Is.). Occurs in forested gullies, particularly on flat ground near streams, or occasionally in open swampy areas.
Hybrids between H. muelleri and H. rugosula– with reddish brown stipes, occasional hairs in the sorus, and sharp, slightly curled lamina hairs (a little longer than those normally found in H. rugosula) but seldom glandular hairs–have been reported from a number of localities in Victoria. Sporangia, as well as the spores, are aborted in some specimens (Brownsey & Chinnock 1987). Possible hybrids between H. muelleri and H. glandulifera–with highly dissected fronds, abundant long lamina hairs and numerous soral hairs–have been found in the Dandenong Ranges.
