Rock Mosses

Black rock-moss Andreaea rupestris, photographed by Sture Hermansson.

Upon first examining the picture above, you might think that you were looking at a patch of moss. Which would not be an unreasonable assumption to make, because that is exactly what you are looking at. But this is not just any moss, but perhaps one of the most interesting mosses out there.

The hundred or so species of the genus Andreaea, found in cooler regions around the world, are commonly known as rock mosses or granite mosses in reference to their preferred growth habitat on acidic rocks. They can often look black or red rather than green (presumably relative to how dry they are), and they are often brittle. Glime (2013) notes that a characteristic feature of granite mosses is that a hand brushed over one will come away with small fragments stuck to it, and suggests that this may act as a method of vegetative dispersal. Usually, granite mosses are autoicous: a single plant has both male and female reproductive structures, but they are borne in separate clusters. What makes Andreaea really interesting, though, is how it produces spores. As explained in the diagram I used in an earlier post, mosses produce spores from a sporophyte (diploid plant) that grows supported by the gametophyte (haploid plant) that comprises the green, vegetative stage of the moss life cycle. In most mosses, the sporophyte holds itself up by means of a long stalk called a seta, and spores are released from the terminal capsule by the ejection of a covering operculum.

Capsules of Andreaea, photographed by David Tng.

Andreaea does things differently. In this moss, the capsule is not supported by its own stalk, but is instead lifted up on an extension of the gametophyte called a pseudopodium. And instead of popping off an operculum, the Andreaea capsule splits open longitudinally into a squashed crown. Andreaea shows its difference after the spores are released as well: while the spores of other mosses germinate into a filamentous protonema (the moss 'seedling', as it were), the protonema of Andreaea bears thalloid appendages.

Such is the distinctive of Andreaea that it has been classified in a separate class from most other mosses, the Andreaeopsida. Phylogenetic analysis has demonstrated that Andreaea is one of the earliest diverging of all mosses, being the next to diverge from the main moss lineage after the Sphagnopsida (the group that includes Sphagnum). In some classifications, the class Andreaeopsida is restricted to Andreaea alone, but there are two other small genera that have been grouped with it in the past.

Andreaeobryum macrosporum, photographed by Masaki Shimamura.

Andreaeobryum macrosporum is a single unusual moss species found in north-west North America. Like Andreaea, it is found growing in rocks, though its preference is for basic rocks such as limestone. It also resembles Andreaea in having a spore capsule that opens through slits, though in the case of Andreaeobryum the apex of the capsule eventually wears off as well and the capsule splays fully open. The biggest difference between Andreaea and Andreaeobryum is that the capsule of the latter is not raised on a gametophytic pseudopodium, but possesses its own supporting seta like that of typical mosses (albeit a particularly short and stubby one). The phylogenetic position of Andreaeobryum remains uncertain: a molecular analysis by Chang & Graham (2011) recovered an Andreaea-Andreaeobryum clade, but with very low support.

Takakia lepidozioides, from here.

The real wild-card in basal moss phylogeny, however, is the little green monster known as Takakia. Takakia is a genus of two species found in western North America and eastern Asia. It was first discovered in the Himalayas and described in 1861—as a liverwort. This is a bit like being presented with a new species of snake, and describing it as a type of eel. But it has to be pointed out that Takakia possesses some very un-moss-like features. It has finely divided leaves, a feature common in liverworts but not known from any other moss. Its leaves contain oil bodies: again, unlike any other moss, but like many liverworts. Matters were not helped by the fact that Takakia was first described from vegetative material only, and it was not until the description of sporophytes in the 1990s that Takakia was conclusively accepted as a moss (Renzaglia et al. 1997).

Even so, its position within the mosses remained uncertain. A relationship with Andreaea has been suggested, as the capsule (though borne on a seta rather than a pseudopodium) opens through a single spiral slit. However, recent phylogenetic analyses have not supported a direct relationship between the two. Chang & Graham (2011) found in the analysis of their data that its position was vulnerable to the analytical model used: it could be placed as the sister taxon to all other mosses, or it could be the sister to the Sphagnopsida (with the two together being the basalmost moss clade). We have not heard the last of little Takakia.

REFERENCES

Chang, Y., & S. W. Graham. 2011. Inferring the higher order phylogeny of mosses (Bryophyta) and relatives using a large, multigene plastid data set. American Journal of Botany 98 (5): 839-849.

Glime, J. M. 2013. Bryophyta - Andreaeopsida, Andreaeobryopsida, Polytrichopsida. Chapt. 2-6. In: Glime, J. M. Bryophyte Ecology. Volume 1. Physiological Ecology. Ebook sponsored by Michigan Technological University and the International Association of Bryologists. Last updated 29 June 2013 and available at .

Renzaglia, K. S., K. D. McFarland & D. K. Smith. 1997. Anatomy and ultrastructure of the sporophyte of Takakia ceratophylla (Bryophyta). American Journal of Botany 84 (10): 1337-1350.

Pitchfork Mosses

Dicranum flagellare, photographed by Sue. The upright green stalks are the brood branches.

The subject of today's post is the cosmopolitan moss genus Dicranum, sometimes known as fork mosses or, apparently, wind-blown mosses. Dicranum species are characterised by elongate narrow leaves and an erect, often forked growth habit. In some habitats, Dicranum species may form reasonably extensive turfs. The genus name comes from the Greek word for a pitchfork and apparently refers to the teeth of the peristome (the ring of teeth around the opening of the spore capsule) though, if this is true, naming these mosses after a feature of the spore capsule may not necessarily have been the best idea. Many Dicranum populations produce sporophytes relatively rarely (a diagram of the moss life cycle was included in this post). Instead, these populations more commonly reproduce asexually through the production of vegetative propagules by the gametophyte. Once such species, the Holarctic Dicranum flagellare, produces terminal clusters of reduced branches, called 'brood branches'. If detached from the parent plant, these brood branches can grow into a new moss. A notable dispersal agent for brood branches, as it turns out, is slugs (Kimmerer & Young 1995). Brood branches break off the parent plant as the slug crawls past them, adhering to the slug by means of its slime. The trail of slime left by the slug also greatly improves the chance of a brood branch adhering to a suitable substrate once it becomes separated from its transport.


Dicranum scoparium, photographed by Li Zhang.

Because of the rarity of sporophytes, species of Dicranum are mostly distinguished by features of the leaves. Dicranum leaves may be straight or curved, the edge of the leaf may be smooth or toothed, and the blade of the leaf may be composed of one or two cell layers. Many species are characterised by the shape of the leaf in transverse section (Hedenäs & Bisang 2004). When sporophytes are produced, Dicranum species are dioicous: that is, they have separate male and female plants. However, in a number of species, the male plants are reduced in size and grow epiphytically on the leaves or rhizoids of the larger female plants. At least one species, Dicranum scoparium, has both dwarf and full-sized males (Hedenäs & Bisang 2004). Some Dicranum species have wide distributions, with a number found almost throughout Eurasia and North America, but others have more restricted distributions (D. transsylvanicum, for instance, is known from a single location in western Romania). Dicranum species are often very selective habitat-wise, with species differing in their choice of habitat, and they have been used as indicators of environmental conditions. This habitat selectivity can result in fragmented species distributions: for instance, Dicranum muehlenbeckii (which grows in dry, calcareous or mineral-rich environments) is found in central Europe, but is also known from a single locality in central Sweden. Dicranum scoparium, a more generalist species found in both humid and dry conditions, is widespread in Eurasia and North America, but is also known from New Zealand and a single region of Australia, near Mt Kosciuszko in New South Wales. As noted in a previous post, much ink has been spilled as regards the biogeographic processes underlying disjunct distributions in moss taxa. In that light, it should be pointed out that, while Australian and New Zealand specimens of Dicranum scoparium do tend to be less robust than the average Holarctic specimen, no molecular differences have yet been identified between the populations (Klazenga 2012).

REFERENCES

Hedenäs, L., & I. Bisang. 2004. Key to European Dicranum species. Herzogia 17: 179-197.

Kimmerer, R. W., & C. C. Young. 1995. The role of slugs in dispersal of the asexual propagules of Dicranum flagellare. The Bryologist 98 (1): 149-153.

Brachythecium salebrosum: Some Like It Temperate

Brachythecium salebrosum, photographed in Slovakia by M. Lüth.

Brachythecium salebrosum is a species of moss found in many temperate regions of the world. It often grows in drier habitats than other mosses; in a study of the effects of human disturbance on forest moss communities in Estonia, B. salebrosum made up slightly less than a tenth of the moss flora in unmanaged forests, but accounted for more than a quarter of the flora in managed forests (Vellak & Paal 1999). Brachythecium salebrosum is known from Eurasia, North America, southernmost Africa and Australasia. Interestingly, it hasn't yet been recorded from South America (Delgadillo 1993), and an explanation for its distribution would need to explain how it came to disperse (or vicariate) between North America and South Africa yet bypass South America and northern Africa. Another oddity in its distribution can be seen in comparison to the similar species Brachythecium rotaeanum: while both species are found in Eurasia and North America, B. salebrosum is more common in the western part of each continent while B. rotaeanum dominates in the east (so as one travels east from Europe, the distribution bands are salebrosum-rotaeanum-salebrosum-rotaeanum) (Ignatov et al. 2008). Some authors (particularly European ones) have expressed scepticism about the distinction between these two species, but they are distinguished by both morphological and molecular characters according to Ignatov et al. (2008).

Individual leaf of Brachythecium salebrosum, photographed by Russ Kleinman & Karen Blisard.

Distinguishing Brachythecium salebrosum from related species is, admittedly, not a simple task. Specimens of this species can vary quite significantly across their range. Generally, however, B. salebrosum has plicate leaves (i.e. they are folded longitudinally like an accordion) that are more or less falcate in shape with serrated margins. There is a clearly distinct group of small subquadrate cells at the lower corners of the leaf. The spore capsules are held more or less horizontally, and the seta supporting the capsule is generally about two centimetres high (Ignatov et al. 2008).

REFERENCES

Delgadillo M., C. 1993. The Neotropical-African moss disjunction. The Bryologist 96 (4): 604-615.

Ignatov, M. S., I. A. Milyutina & V. K. Bobrova. 2008. Problematic groups of Brachythecium and Eurhynchiastrum (Brachytheciaceae, Bryophyta) and taxonomic solutions suggested by nrITS sequences. Arctoa 17: 113-138.

Vellak, K., & J. Paal. 1999. Diversity of bryophyte vegetation in some forest types in Estonia: a comparison of old unmanaged and managed forests. Biodiversity and Conservation 8: 1595-1620.

Mosses Have a Place for Reproduction

A Rhizogonium photographed in the Philippines by Leonardo L. Co.

The Rhizogoniaceae are a family of mosses found in tropical and subtropical parts of the world, with a concentration of diversity in the Southern Hemisphere. Many species in the family are epiphytic; in particular, many show a preference for growing on the trunks of tree ferns (O'Brien 2007). The family has been defined by features such as sharply toothed, usually bistratose (i.e. with two cell layers) leaves and sporophytes located in the basal half of the erect stems, but molecular studies have indicated that the Rhizogoniaceae in the broad sense are para- or polyphyletic, and for this post I'll be using Rhizogoniaceae in a more restricted sense, corresponding to the 'clade C' of O'Brien (2007), including genera such as Rhizogonium, Cryptopodium, Calomnium, Goniobryum and Pyrrhobryum. One member of the Rhizogoniaceae, Pyrrhobryum dozyanum, is often used in moss gardens (it appears that there may also be a moss doing the rounds under this name in the European aquarium trade, though I haven't found anything to confirm whether this species, also being referred to as "Mayaca fern" or "Indonesiae bogoriensis", is actually P. dozyanum. Many bryophytes and other such plants in the aquarium trade have been misidentified, sometimes dramatically so).

View under microscope of leaf of Pyrrhobryum dozyanum, showing the toothed margins characteristic of Rhizogoniaceae. Image from here.

Most attention on Rhizogoniaceae from an evolutionary point of view has focused on what they might say about the relationship between acrocarpy and pleurocarpy. To explain what these terms mean, we'll start with the following diagram (from here):

Like other plants, mosses go through an alternation of generations, with both haploid and diploid multicellular stages. The haploid stage of the life cycle, the gametophyte, is the leafy green part of the moss. The gametophyte produces perichaetia, whorls of modified leaves within which the gamete-producing organs are contained. When a female gamete is fertilised, the resulting diploid zygote grows into the sporophyte, the brown thread-like structure you will often see growing out of a moss. The sporophyte produces haploid spores that will be dispersed to grow into new leafy gametophytes.

The diagram above shows an acrocarpous moss, in which the perichaetium is produced at the end of a growing branch of the gametophyte. Other mosses, however, are pleurocarpous, with perichaetia produced on the side of a branch. Whether a moss is acrocarpous or pleurocarpous is one of the first things a botanist will look at when attempting to identify it. However, many Rhizogoniaceae do not easily fall on either side of the acrocarpous/pleurocarpous distinction. They are what is called cladocarpous: the perichaetia are produced at the ends of small side-branches. However, lest any moss enthusiasts accuse me of overly simplifying things, I must point out that a great deal has been written on the exact distinctions between acrocarpous vs cladocarpous vs pleurocarpous. Like so many distinctions in nature, there are examples that blur the distinction between these states. As the perichaetia-bearing side-branches in a cladocarpous moss get progressively shorter, they become less and less distinguishable from pleurocarpy. In light of this, recent authors have suggested that the distinction between cladocarpy vs pleurocarpy should be defined by whether or not the side-branch bearing a perichaetium also bears normal vegetative leaves. If it only bears perichaetial leaves, then it is pleurocarpous: by this definition, some Rhizogoniaceae (including the genus Rhizogonium) are truly pleurocarpous (Bell & Newton 2007).

Goniobryum subbasilare, photographed by David Tng.

The vast majority of pleurocarpous mosses belong to a clade called the Hypnanae, which is massively speciose (probably about half of living mosses are hypnanaens). Because the hypnanaen mosses are so successful, there is a lot of interest in their relationships with other mosses. And as it turns out, the Rhizogoniaceae (with their combination of cladocarpous and pleurocarpous members) are closely related to the Hypnanae. Indeed, the Hypnanae are nested within the older, paraphyletic grade referred to the Rhizogoniaceae (O'Brien 2007). The acrocarpous state is the plesiomorphic one for mosses, with cladocarpy evolving in numerous lineages. Pleurocarpous mosses, it seems likely, have then evolved from cladocarpous ancestors, though either a number of times or with a number of reversals.

REFERENCES

Bell, N. E., & A. E. Newton. 2007. Pleurocarpy in the rhizogoniaceous grade. In: Newton, A. E., & R. S. Tangney (eds) Pleurocarpous Mosses: systematics and evolution pp. 41-64. CRC Press.

O'Brien, T. J. 2007. The phylogenetic distribution of pleurocarpous mosses: evidence from cpDNA sequences. In: Newton, A. E., & R. S. Tangney (eds) Pleurocarpous Mosses: systematics and evolution pp. 19-40. CRC Press.

The Trials and Tribulations of Tree Moss

Weymouthia cochlearifolia, photographed by Juan Larraín.

The Lembophyllaceae are a family of mosses found most abundantly in the Australasian region, though species are also found in other parts of the world such as Asia and South America. Most members of the family are epiphytic (growing on trees) or epilithic (growing on rocks). The composition of the family has varied significantly over the years, and as currently circumscribed the various Lembophyllaceae lack any reliable shared morphological characters and are united on the basis of molecular data (Olsson et al. 2009). Lembophyllaceae usually have concave leaves, loosely appressed to terete shoots, that lack a clearly differentiated leaf margin (Olsson et al. 2009).

Capsules of Isothecium alopecuroides, photographed by Hermann Schachner.

In the broader context, Lembophyllaceae are placed among the pleurocarpous mosses of the order Hypnales ('pleurocarpous' means that the reproductive structures are produced on small side branches rather than at the top of the main stalk), probably as the sister group to the bulk of the Neckeraceae (Olsson et al. 2009). Merget & Wolf (2010) reported finding Lembophyllaceae as polyphyletic but a closer look at the supplementary figures shows that only two of their four clades ('Lembophyllaceae III' and 'IV') actually correspond to the current concept of the family established by Quandt et al. (2009); the remainder represent genera removed to other families. More to the point, Merget & Wolf were using that most wretched of molecular methods, neighbour joining, and despite their use of a large number of source taxa it is difficult to accord their results much significance.

Spruce trees with a covering of Isothecium myosuroides in Olympic Natural Park, USA. Photo from here.

One genus of Lembophyllaceae, Weymouthia, contains two species found in Australia, New Zealand and South America. Such disjunct distributions have been the subject of much debate in moss biogeography. Some authors attribute them to a Gondwanan ancestry, indicating that the modern species must have arisen prior to the separation of these landmasses through continental drift. Others would see them as the result of post-separation dispersal. Supporters of the former explanation point to the supposed inability of moss spores to survive extended environmental exposure, and the correlation of numbers of shared species with age of geological separation rather than current distance (Blöcher & Frahm 2002; e.g. South America shares more species with New Zealand than southern Africa, despite being closer geographically to the former). Supporters of the latter point to the low levels of morphological and molecular differentiation between individuals from disjunct populations.

REFERENCES

Blöcher, R., & J.-P. Frahm. 2002. A comparison of the moss floras of Chile and New Zealand. Tropical Bryology 21: 81-92.

Merget, B., & M. Wolf. 2010. A molecular phylogeny of Hypnales (Bryophyta) inferred from ITS2 sequence-structure data. BMC Research Notes 3: 320.

Olsson, S., V. Buchbender, J. Enroth, S. Huttunen, L. Hedenäs & D. Quandt. 2009. Evolution of the Neckeraceae (Bryophyta): resolving the backbone phylogeny. Systematics and Biodiversity 7 (4): 419-432.

Quandt, D., S. Huttunen, R. Tangney & M. Stech. 2009. Back to the future? Molecules take us back to the 1925 classification of the Lembophyllaceae (Bryopsida). Systematic Botany 34 (3): 443-454.

Mosses: Not as Simple as You Think (Taxon of the Week: Ectropothecium)

Ectropothecium sandwichense, a moss species with a scattered, mostly tropical distribution on islands in the South Pacific. Photo from here.

I have to admit to becoming increasingly glad that I don't work on mosses. The new Taxon of the Week is a moss, and looking up stuff on it has driven me into a strange world of unfamiliar terminology and fine-scale features. If I mess anything up here, I only hope that the legions of moss fans out there* forgive my transgressions.

*Do not doubt that they're out there. As I've commented before, bryologists are a dedicated bunch.

Ectropothecium is a genus of mostly hydrophytic mosses found worldwide (hydrophytic plants grow either in water or in completely waterlogged soil; some Ectropothecium species do the former, others the latter). It belongs to a clade of mosses known as the pleurocarpous mosses; while other (acrocarpous) mosses branch only rarely and produce terminal archegonia (the female reproductive organs - see the diagram at the posts linked to above) at the end of the stem, pleurocarpous mosses produce lateral archegonia on highly branched and extensively interwoven stems (Shaw & Renzaglia, 2004). Pleurocarpous mosses are divided molecularly into three orders, Ptychomniales, Hookeriales and Hypnales; Ectropothecium belongs to the Hypnales which have a smooth spore capsule with a calyptra (protective cap) that usually opens by splitting along one side (Buck et al., 2004). Within the Hypnales, Ectropothecium is placed in the family Hypnaceae; however, phylogenetic studies of Hypnales (e.g. De Luna et al., 2000) suggest that members of the Hypnaceae may be para- or polyphyletically placed within the order.


Ectropothecium zollingeri, a species with a distribution centred in south-east Asia. Photo from here.

Ectropothecium itself is distinguished by having spore capsules that are very small (usually less than 1 mm long) and almost spherical (Buck & Tan, 2008), non-decurrent leaves (not extending down the stem where they join), short and broad leaf cells and filamentous pseudoparaphyllia that are two or three cells wide at the base (Ireland, 1992). Pseudoparaphyllia are small outgrowths of the stem that cluster around the base of new side-branches (as opposed to paraphyllia which are normally scattered more evenly along the entire stem); they may be thread- or blade-shaped. See Ignatov & Hedenäs (2007) for a review of the distinctions between paraphyllia, pseudoparaphyllia and proximal branch leaves, though to be honest if you understand the difference you're somewhat ahead of me (as far as I can tell, pseudoparaphyllia grow on the stem around the primordium of a new branch and remain on the stem, while proximal branch leaves may start growing around the primordium but end up being transferred to the new branch).

REFERENCES

Buck, W. R., C. J. Cox, A. J. Shaw & B. Goffinet. 2004. Ordinal relationships of pleurocarpous mosses, with special emphasis on the Hookeriales. Systematics and Biodiversity 2 (2): 121-145.

Buck, W. R., & B. C. Tan. 2008. A review of Elmeriobryum (Hypnaceae). Telopea 12 (2): 251-256.

De Luna, E., W. R. Buck, H. Akiyama, T. Arikawa, H. Tsubota, D. González, A. E. Newton & A. J. Shaw. 2000. Ordinal phylogeny within the hypnobryalean pleurocarpous mosses inferred from cladistic analyses of three chloroplast DNA sequence data sets: trnL-F, rps4, and rbcL. Bryologist 103 (2): 242-256.

Ignatov, M. S., & L. Hedenäs. 2007. Homologies of stem structures in pleurocarpous mosses, especially of pseudoparaphyllia and similar structures. In Pleurocarpous Mosses: systematics and evolution (A. E. Newton & R. Tangney, eds) pp. 227-245. The Systematics Association Special Volume Series 71. Taylor& Francis / CRC Press: Boca Raton.

Ireland, R. R. 1992. Studies of the genus Plagiothecium in Australasia. Bryologist 95 (2): 221-224.

Shaw, J., & K. Renzaglia. 2004. Phylogeny and diversification of bryophytes. American Journal of Botany 91 (10): 1557-1581.

Southern Moss (Taxon of the Week: Ptychomitrium muelleri)

There don't seem to be any images of Ptychomitrium muelleri available online, so here's another Ptychomitrium species, P. gardneri from China. Photo by Li Zhang.

Mosses are often treated as the poor relation in plant diversity. Popular presentations of plant evolution often tend to have even more of a Scala Natura-esque slant to them than presentations of animal evolution, and so mosses and other non-vascular plants get glossed over as mere stepping stones to their more upright "descendants", if they even warrant a mention at all. This is, of course, complete rubbish - mosses have a very respectable diversity of species (about 10,000, according to Tree of Life). I've met a few moss researchers over the years, and a more devoted following a taxon could not hope for.

Ptychomitrium muelleri is a haplolepidous moss of the family Ptychomitriaceae (I'll explain what that means in a minute). It grows to a maximum height of one and a half centimetres, and if the type specimens are any indication, prefers to grow on rocks. Ptychomitrium mosses seem to be found more or less worldwide, but Ptychomitrium muelleri itself is found in south-eastern Australia, New Caledonia, southern South America and southernmost Africa. What is interesting about this species' distriution is that it was thought to be endemic to Australia until very recently when Cao et al. (2001) established that species described from each of the other localities were conspecific with P. muelleri. As a result, P. muelleri has what might be described as a classic "Gondwanan" distribution, but I rather doubt that Gondwana had anything to do with it. After all, moss spores are very light and extremely easily dispersed, and surely it is no coincidence that all the localities where P. muelleri can be found lie roughly along the same wind belt.



The diagram of a moss life cycle above has been stole from Palaeos.com. For the nonce, the important details are these - mosses, like other plants, are multicellular at both the haploid and diploid stages of the life cycle, but unlike vascular plants, the larger, dominant stage of the life cycle is the haploid gametophyte. When a female gametophyte is fertilised, the diploid sporophyte remains attached to the gametophyte and grows a spore-filled capsule that eventually breaks open (after the loss of the protective calyptra) to release the spores. Around the mouth of the capsule is a ring of "teeth", the peristome. In basal mosses, the peristome is made up of entire cells, but in the class Bryopsida, the arthrodontous mosses (which includes the larger part of the mosses), the teeth are reduced to cell wall remnants. Most of the bryopsid lineages have two rows of teeth in the peristome, an outer and an inner, but Ptychomitrium belongs to a group called the Haplolepideae or Dicranidae which have only the inner row of teeth. The haplolepidous mosses form a monophyletic clade within the Bryopsida.


Ptychomitrium polyphyllum from Scotland, showing the calyptra on the left capsule and the exposed peristome on the right. Photo from here.

Most of the features separating moss taxa are microscopic and relate to such things as cell arrangement (which is my weaselly method of saying that I don't understand a word of them), but Ptychomitrium is distinguished by having a mitrate calyptra (and those unsure what "mitrate" means might want to look at the Taxon of the Week post of two weeks ago) with characteristic lobes around the lower edge (Hernández-Maqueda et al., 2008, compare it to a Hawaiian skirt). Ptychomitrium muelleri has (amongst other features) lingulate (tongue-shaped, I'm guessing) leaves with smooth margins, and ovoid capsules.

REFERENCES

Cao, T., S. Guo & Y. Zhang. 2001. Distribution of Ptychomitrium muelleri (Bryopsida), with its synonyms. The Bryologist 104 (4): 522-526.

Hernández-Maqueda, R., D. Quandt, O. Werner & J. Muñoz. 2008. Phylogeny and classification of the Grimmiaceae/Ptychomitriaceae complex (Bryophyta) inferred from cpDNA. Molecular Phylogenetics and Evolution 46 (3): 863-877.