BFNA Title: Haplodontium
Author: J. Spence 
Date: February 21, 2008
Edit Level: R 
Version: 1

Bryophyte Flora of North America, Provisional Publication
Missouri Botanical Garden

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XX. HAPLODONTIUM Hampe, Ann. Sci. Nat., Bot. ser. 5(4): 336. 1865  * [Latin haplo, single, and dontium, tooth, the peristome is single]


John Spence


Plants small, in open to dense turfs or sometimes as scattered individuals, light green to pink-green, often brown proximally. Stems 0.5--2(--3) cm, evenly foliate, unbranched to freely branched by subfloral innovations, stolons absent; often densely tomentose proximally, macronemata absent, rhizoids sparse to abundant. Leaves somewhat twisted or contorted to subsecund or sometimes imbricate when dry, erect to erect spreading when wet; elliptic, ovate to oblong or sometimes broadly lanceolate, not decurrent; margins plane or narrowly revolute below, 1-stratose, limbidium absent, distal margins smooth or rarely weakly serrulate, apex rounded-obtuse to broadly acute, apiculus absent or occasionally present, costa subpercurrent to percurrent or rarely excurrent, transverse section typically lacking guide cells, adaxial supracostal cells elongate, similar to adjacent laminal cells, laminal cells rather uniform, elongate and thin walled, lax, rhomboidal to elongate-rhomboidal, 40--120 x 10-20 \um, not pitted, distal cells not oblique to costa, alar cells irregularly short- to long-rectangular, but not distinctly differentiated. Specialized asexual reproduction absent. Sexual condition dioicous; perigonia and perichaetia usually appearing lateral due to rapid innovation growth, leaves the same size as or somewhat smaller than vegetative leaves. Seta single, yellow- to red-brown, 3--12 mm, curved to flexuose. Capsule erect, suberect to nutant, subglobose to broadly pyriform, often somewhat obscured by elongate innovations, 1--2.5 mm, sometimes curved or irregularly shaped, hypophysis not enlarged or inflated, exothecial cells irregularly quadrate to short-rectangular; operculum flat to weakly convex, apiculate or umbonate; peristome single, typically exostomial but sometimes of unknown origin, absent, or rarely double, teeth slender, irregularly linear-lanceolate, hyaline, sometimes perforate, smooth or finely papillose. Spores small, 10--20(--24) \um, pale, smooth or finely papillose, not shed in tetrads.


Species ca. 40 (2 in the flora): pantropical, subtropical to temperate, centered in the mountains of Africa and South America, but extending to Eurasia, North America, and the Pacific.


Because of previous over-reliance on the peristome, the taxonomy of Haplodontium and Mielichhoferia remains confused.  The gametophytes of the two genera are very unlike, with Haplodontium species similar to those of Plagiobryum and Plagiobryoides. Recent genetics research has clearly shown that Mielichhoferia is related to Pohlia, while the species centered around H. macrocarpum are closer to Bryum and relatives.  As our two species are very similar gametophytically to the type of Haplodontium, H. megalocarpum Arnott, I have chosen to place them in Haplodontium. Peristome reduction is common and complex in this genus, from double to single to absent.


SELECTED REFERENCES: Brassard, G.R. and T. Hedderson. 1983. The distribution of Mielichhoferia macrocarpa, a North American endemic moss. Bryologist 86: 273--275. Shaw, J. and H. A. Crum. 1984. Peristome homology in Mielichhoferia and a taxonomic account of North American species. J. Hattori Bot. Lab. 57: 363--381. Showers, D. 1980. Mielichhoferia tehamensis, sp. nov., from northern California. Bryologist 83: 365--366.


1. Peristome present, operculum plane or weakly convex, sometimes apiculate; leaf margins narrowly revolute, at least proximally, distal lamina cells at tip elongate; leaves somewhat twisted or secund when dry ........... 1. Haplodontium macrocarpum


1. Peristome lacking; operculum umbonate; leaf margins plane throughout, distal lamina cells at tip short-rectangular to subquadrate; leaves imbricate, stem julaceous …..…2. Haplodontium tehamense


1. Haplodontium macrocarpum (Hooker) Spence, Phytologia 87: 26. 2005


Weissia macrocarpa Hooker, Musci Americani; or, Specimens of the Mosses Collected in British North America, 74. 1828; Mielichhoferia macrocarpa (Hooker) Bruch & Schimper ex Jaeger & Sauerbeck


Plants pale light green to pink-green, red-brown to brown proximally. Stems 0.5--3 cm, weakly to strongly branched, not julaceous. Leaves  flexuose to weakly secund when dry,  erect when wet, ovate to oblong or broadly lanceolate, 0.6--2 mm; margins narrowly revolute proximally, apex broadly acute to sometimes acuminate, apiculus absent or rarely present, costa subpercurrent to percurrent, pale tan-brown or red, rarely excurrent in short to medium-length hairpoint, laminal cells rather uniform, elongate and thin walled, lax, rhomboidal to elongate-rhomboidal, 40--120 x 10--18 \um, cells near leaf tip usually elongate, 3:1 or more, cells somewhat narrower along margin but not forming a distinct limbidium. Seta single, yellow-brown, 4--12 mm, curved to flexuose. Capsule erect to nutant, subglobse to short-pyriform, 1.3--2.5 mm, operculum flat to weakly convex, weakly apiculate, peristome single, teeth slender, irregularly linear-lanceolate, hyaline, sometimes perforate, smooth or finely papillose. Spores small, 12--20(--24) \um, pale, smooth or finely papillose.


Capsules mature summer (Jul--Aug). Rare on damp to seepy rock faces or crevices, typically limestone; 0--3500 m, in southern latitudes restricted to high elevations; widely disjunct, Arctic-alpine; Greenland; Alta, Nfld., Nunavut; Alaska, Colo., Mont., Utah; Eurasia (ne Russia). A species of conservation concern.


Although Haplodontium macrocarpum has been thought to be associated with mineral-rich rock, collections come from a wide variety of rock types.  In the Southern and Central Rocky Mountains it is apparently restricted to limestone. Some specimens from the Aleutian Islands have a stongly excurrent costa, and in some respects approach the Asian Mielichhoferia (Haplodontium) himalayana Mitten.


2. Haplodontium tehamense (Showers) Spence, Phytologia 87: 26. 2005


Mielichhoferia tehamensis Showers, Bryologist 83: 365, figs. 1--3. 1980


Plants shiny light green to yellow-green or white-green, light brown below. Stems 0.5--1 cm, stongly branched, somewhat julaceous. Leaves imbricate when dry, erect to erect-spreading when wet; elliptic to  oblong, 0.5--1 mm; margins plane, apex rounded-obtuse to broadly acute, apiculus absent, costa subpercurrent, yellowish, laminal cells rather uniform, elongate and thin walled, lax, rhomboidal to elongate-rhomboidal, 40--80 (--100) x 10--20 \um, distal cells at tip shorter, irregularly short-rectangular to subquadrate. Seta red-brown, 3--7 mm, flexuose. Capsule horizontal to nutant, short and broadly pyriform, 1.2--2.5 mm, operculum convex and umbonate, peristome absent. Spores small, 10--14 \um, pale, more or less smooth.


Capsules mature summer (Aug.). Rare in crevices of volcanic rock in montane areas; 2200--2600 m; Calif. A species of conservation concern.

Haplodontium tehamense is a distinctive species, with its eperistomate capsule and somewhat julaceous stems. It is still only known from a few locations in Lassen Volcanic National Park.