Macromitrium Brid.

The following generic description is modified from Vitt (1983) and Vitt & Ramsay (1985a).

Plants slender to robust, yellow-green, olive-green or rust-brown above, darker below, in dense or loose, spreading, tomentose mats on bark or rock. Stems creeping, with numerous ascendant, simple or forked branches, rather sparsely beset below with much-branched, usually red-brown, and papillose rhizoids, in cross-section with thick-walled outer cells and no central strand. Branch leaves contorted, spirally-twisted, or crisped-flexuose, rarely loosely erect-appressed, apices inrolled to twisted when dry, erect-spreading to squarrose-recurved when moist, linear-lanceolate, ligulate, oblong, ovate-oblong, or lingulate, rounded-obtuse, acute, to long-acuminate, sometimes cuspidate, apiculate, subulate, or long-awned, rarely (but frequently in N.Z. species) with fragile tips, keeled; margins erect, plane, or reflexed-recurved, entire, crenulate to serrate; upper laminal cells rounded to rectangular-elliptic, flat to strongly bulging, smooth to multi-papillose, usually with conical or rounded papillae, ± thick-walled, c. 6–14 μm in greater diam.; basal cells usually differentiated, elongate or rarely short-rectangular, often thick-walled, smooth or tuberculate, sometimes with sinuose lumina. Costa single, prominent, excurrent or ending near or in the apex. Gemmae rare.

Sexuality various (autoicous, dioicous, or pseudautoicous). Perichaetia terminal on short to well-developed lateral branches; perichaetial leaves often longer than vegetative leaves. Perigonia gemmiform, axillary or on short branches, often produced on epiphyllous and dwarf male plants. Setae elongate or less often short, smooth or papillose, erect to flexuose, either dextrorse or sinistrorse; capsules exserted (in all N.Z. species) or rarely immersed, ovate, elliptic, or cylindric, erect and becoming slightly curved when old, smooth or ribbed, usually not constricted below the mouth, abruptly to gradually contracted to the setae by a short neck; exothecial cells thick-walled; stomata superficial, restricted to the lower portion of capsule, often with guard cells poorly differentiated; annulus usually of 1–3 rows of thin-walled cells; operculum rostrate from a conic base. Peristome diplolepideous, double, single, or lacking; exostome teeth 16 and sometimes paired, rarely membranaceous, mostly densely papillose or papillose-striate, erect or recurved when dry; endostome when present consisting of a delicate, sparsely papillose membrane, rarely divided into segments. Calyptra mitrate, rarely splitting along one rib, hairy or naked, covering more than ¾ of the capsule, plicate or laciniate. Spores 1-celled, isosporous or anisosporous, papillose.

A very large genus of perhaps more than 400 spp. distributed mostly in tropical and subtropical regions. Thirteen species and one variety (M. longirostre var. ramsayae (Vitt) comb. nov.) are accepted here in the N.Z. flora, including a single species (M. incurvifolium (Hook. & Grev.) Schwägr.) that is recorded only from the Kermadec Is.

The N.Z. species have been treated in detail by Vitt (1983) with further information provided by Vitt & Ramsay (1985a; 1985b). The taxonomic concepts and species descriptions presented here are largely derived from these publications. In general I have agreed with (and verified) Vitt’s descriptions but have altered their format and simplified them. I have generally not altered Vitt's peristome descriptions.

Despite the availability of Vitt’s revision, Macromitrium in N.Z. remains a difficult genus and some collections, particularly if sterile, defy confident identification. The limits and variability of M. prorepens and M. longirostre are particularly intractable. The variation of some other species (e.g., M. gracile) is great and often confusing. The allied and distinctive pair of M. ligulare and M. ligulaefolium are, in my opinion, nameable to species only when fertile. On the other hand, species such as M. brevicaule, M. grossirete, M. longipes, and M. orthophyllum are well delimited and easily recognised, even in the field, with or without capsules. The species distributions given for the genus are derived from confirmed specimens and by reference to Vitt's (1983) maps.

The ornamentations of the laminal cells in this genus are often more easily observed under the microscope after the leaves have been soaked in lactic acid for 15–30 minutes and then mounted in water.

Vitt & Ramsay (1985a) used a cladistic analysis based on morphological features to assign the Australasian species to seven groups (see pp. 327 and 444–447). Their analysis remains the most detailed of the relationships of Australasian Macromitrium spp. and it is summarised below (including only the N.Z. taxa), following their Table l. For comparability M. ramsayae and M. submucronifolium are cited at the rank given to them by Vitt & Ramsay.

Macromitrium pusillum Mitt. (1859) is a name that has been applied to N.Z. herbarium material of M. ligulare by some authors, including Sainsbury. Vitt & Ramsay (1985a, p. 406; see also Vitt 1983, p. 74) considered the type of the Mitten name to be an Archer Tasmanian collection and M. pusillum Mitt. to be a taxonomic synonym of the widespread Australian (including Tasmania) endemic M. archeri Mitt. in Hook.f. Macromitrium pusillum is not discussed further here.

Macromitrium submucronifolium Müll.Hal. & Hampe (1855) is treated here as inseparable from M. prorepens for reasons discussed below.

Macromitrium ramsayae Vitt (1983) is reduced here to a variety of M. longirostre for reasons discussed below.

Macromitrium wellingtonianum Vitt (1983, p. 61) is rejected from the N.Z. flora. The identity and status of this species in N.Z. has been problematic since its description. Vitt cited a type collected by Balázs at "Tararua Range, 60 km North of Wellington, 800 metres elev.," on 28 Dec. 1972. Dr. Dénes Balázs was a Hungarian geographer who collected bryophytes for the EGR herbarium. In 1972–73 Balázs travelled in the Philippines, New Guinea, eastern mainland Australia and N.Z. (T. Pócs, pers. comm., 5 May 2011). Vitt & Ramsay (1985a, p. 411) subsequently placed M. wellingtonianum in the synonymy of M. angulatum Mitt., a species with a Samoan type. Macromitrium wellingtonianum/angulatum has not been re-found in N.Z. for over 40 years, despite it being a morphologically distinctive species in a N.Z context. The Tararua Range has been assiduously collected in recent years by capable collectors. Rodney Lewington has made dedicated but unsuccessful trips to relocate M. wellingtonianum at its type locality. The most likely explanation for the alleged Tararua collection is that it is an incorrectly labelled specimen gathered elsewhere (probably in P.N.G.) during Balázs’s 1972–73 travels. Dale Vitt (pers. comm., 5 May 2011) considers N.Z. to be "well out of the range of the angulatum group" and believes that the Tararua Range is a "mistaken locality".