Herzogobryum atrocapillum (Hook.f. & Taylor) Grolle
Gymnomitrium atrocapillum Hook.f. & Taylor in Taylor, London J. Bot. 5: 258. 1846. Jungermannia atrocapilla (Hook.f. & Taylor) Taylor & Hook.f. in Hook.f., Bot. Antarc. Voy. 2: 423. 1847. Cesia atrocapilla (Hook.f. & Taylor) Mitt., Phil. Trans. Roy. Soc. London 168: 43. 1879. Cesiusa atrocapilla (Hook.f. & Taylor) Kuntze, Revis. Gen. Pl. 834. 1891. Acolea atrocapillum (Hook.f. & Taylor) Steph., Sp. Hepat. 2: 4. 1901. Herzogobryum atrocapillum (Hook.f. & Taylor) Grolle, Oesterr. Bot. Z. 113: 228. 1966.
Type: Kerguelen, Foul Haven, 200 m, Hooker.
Gymnomitrium marionense S.W.Arnell, Svensk Bot. Tidskr. 47: 415. 1953.
Type: Marion Is., Rand 3788.
Plants thread-like, hair-like, nearly terete, vermiform (due to uniformly appressed leaves), creeping but lateral branches (often ♂ or ♀) often ascending, usually deep red-brown to piceous (but with hyaline margins of leaves), even in sheltered sites rarely green, the intramarginal sector of leaves and the median sector of perianths with red-brown or brownish pigmentation, the leafy shoots very narrow, 125–145 µm in diam., occasionally 160–165(170) µm in diam., with the imbricate and appressed leaves so closely applied as to be almost indistinguishable, but when dry the shoots obscurely laterally keeled due to the somewhat keeled leaves (usually perceptible only on cleared shoot apices). Branching freely occurring, irregular, the branches (evidently) all lateral-intercalary; geotropic, microphyllous axes lacking. Stems rigid, thick for shoot size, the cortical cells firm-walled, feebly differentiated, in 1.5–2 layers of thick-walled cells slightly larger in average diameter than the thick-walled, colorless medullary cells. Rhizoids very few, scattered, limited to older shoot sectors, colorless. Leaves in lower shoot sectors scale-like, often becoming bleached, those above densely erect-appressed (the entire leaf tightly appressed), the stem nowhere visible in dorsal aspect, the leaves almost transversely to weakly succubously inserted, the insertion lines extended across stem midline (the lateral merophytes interlocking), the leaves in basal two thirds strongly concave and with a rounded, ± gutter-like “keel” (in dried state the leaves contracted at the apex and ± keeled); leaves broadly ovate, impossible to flatten without tearing, emarginate to bilobed to 0.15–0.2, the distal portion of leaves tending to be loosely folded, obscurely keeled, sometimes connivent and somewhat dorsally secund (thus, in situ, the leaves collectively forming a ± flat dorsal surface of the shoot, the shoot strongly convex on the ventral surface only); lobes short, triangular, their margins often incurved, largely decolorate and leaf margins proximal to lobes hyaline-margined, the hyaline marginal cells thin-walled, often erose with age, forming prominent denticulations. Leaves with marginal cells differentiated, thin-walled, bleached and empty, forming a border 1–2 cells wide, even on young leaves, the marginal cells variable, but often radially somewhat elongated (and 9–11 × 15–22 µm), their ends narrowed, projecting and lending the margins crenulate, rounded at the summit; lamina cells conspicuously and evenly thick-walled, lacking trigones, the lumina angular-rounded, the cells small, 10–15 × 11–18 µm, the cells toward leaf base somewhat larger, to 13–16 × 16–20 µm; surface smooth. Underleaves lacking, the ventral merophytes very narrow.
Dioecious. Androecia often on lateral branches of limited length, terminal but becoming intercalary, the shoots often repeatedly androecial; bracts mostly in 2–4 pairs (the leaves below the androecia gradually larger and grading into the bracts), dorsally assurgent, slightly saccate, strongly ventricose, the apices contracted and appearing somewhat beaked; antheridia solitary. Gynoecia terminal on mostly lateral branches of varying length, if fertilized never innovating (but often with a lateral-intercalary branch from lower down on the gynoecial axis); bracts much larger than leaves, together with the perianth forming a clavate, abruptly enlarged, capitulum 3–3.5× wider than sterile shoot sectors, bracts broadly ovate or ovate-deltoid, bilobed to 0.2–0.3, when young hyaline-margined but at maturity becoming erose-margined, the margins strongly serrulate-denticulate with elongated, in part finger-like cells; bracteole lacking (or ?vestigial). Perianth long-ovoid, widest in basal third and gradually narrowed, green basally, brown pigmented in median third, contracted at mouth, the apical 0.2–0.35 bleached, strongly pluriplicate, the mouth cells fragile and easily broken, mostly in broken condition.
Sporophyte not seen.
Distribution and Ecology : Circumsubantarctic; New Zealand: South Island; Heard Island (Bergstrom and Selkirk, 1997), Kerguelen Island, Crozet Island, Marion Island, Prince Edward Island, Antarctica (Bouvetoya, South Orkney Islands; cf. Bednarek-Ochyra et al., 2000). In New Zealand known only from the Scotts Track station (Arthur’s Pass Natl. Park, South Island), reported by Schuster (1996d).
Comments : Plants are thread-like (typically at most 140 µm wide), and due to the uniformly appressed leaves, are markedly vermiform. The leaves are imbricate and so closely appressed as to be nearly indistinguishable; when dry, the distal portions are folded together lending the leaves obscurely keeled above. The leaves are emarginate to short-bilobed, 18–20 cells wide, with intramarginal cells equally thick-walled and only 9–13 × 10–18 µm.
