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Schistidium urnulaceum

Interesting Facts

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Description

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Family Grimmiaceae

Plants acrocarpous or cladocarpous , small to large, usually olivaceous to blackish green, growing in rigid cushions , tufts, mats or patches. Stems erect , ascending , or prostrate , dichotomously to irregularly branched. Leaves erect and tightly appressed to crisped when dry, erect-spreading to patent when wet, lanceolate to ovate-lanceolate, less often ovate , oblong-ovate, linear , or lingulate , keeled , canaliculate , to broadly concave , smooth or sometimes longitudinally plicate , rarely with adaxial lamellae (Indusiella), margins plane , incurved , or variously recurved or revolute , mostly entire, 1- to multistratose, acuminate, acute to rounded-obtuse, typically with a hyaline awn , sometimes muticous , costa single, rarely spurred or forked distally (Codriophorus and Niphotrichum), usually strong , percurrent to excurrent, rarely subpercurrent, typically with one stereid band , distal lamina 1-2(-4) -stratose; basal cells quadrate to elongate , rarely oblate , straight, sinuose, or nodulose , basal juxtacostal and marginal regions usually differentiated, alar cells undifferentiated or hyaline; mid leaf cells quadrate to elongate, commonly sinuose or sinuose-nodulose, usually thick-walled. Perichaetia terminal on tips of stems or lateral branches; perichaetial leaves differentiated or not. Seta short to long, smooth or rarely papillose . Capsule usually erect, usually ovoid , obloid , cylindrical or cupulate , symmetric or rarely strongly ventricose at the base and gibbous , smooth or sulcate ; annulus present or absent, often compound , deciduous or persistent ; operculum mammillate to long-rostrate, sometimes attached to the columella after dehiscence (most Schistidium) ; peristome present, seldom rudimentary or absent, consisting of 16 teeth, lanceolate to linear, entire, perforated or cribrose, variously split into 2 or 3 unequal prongs or divided nearly to the base into two filiform somewhat paired segments, smooth or variously ornamented. Calyptra small to large, covering only the operculum to half or more of the capsule, cucullate , mitrate, or mitrate-campanulate, smooth or plicate, naked, sometimes papillose, slightly to distinctly lacerated or deeply lobed at the base. Spores globose , smooth or papillose.

Genera ca. 11, species ca. 325 (9 genera, 109 species in the flora ) : worldwide.

Most species in the Grimmiaceae are xerophytic and colonizers of bare, usually dry and exposed rocks and stones , forming predominantly dark green to blackish cushions or tufts. However, some species occur on wet or damp rocks along watercourses and lakes or in seepage sites. They rarely inhabit soil and only a few species are epiphytes.

The Grimmiaceae is classically distinguished by quadrate to short-rectangular mid leaf cells typically sinuose to nodulose and thick-walled, and leaves usually awned , often with the awns long and toothed or papillose. There is a wide range of variation . While awns are present in most species, length varies from a short, translucent apiculus to exceeding the length of the lamina. Awns can be flat or terete , smooth or denticulate , spinose or papillose, and long-decurrent or not. Similarly, mid leaf cells range from oblate to long-rectangular and sinuose to almost straight. The range of variation in these characters makes it difficult to describe this family in simple and unequivocal terms .

The generic classification within the Grimmiaceae has long been a subject of controversy. In traditional treatments the family is considered to include the two largest genera, Grimmia and Racomitrium, with several peripheral, mostly mono- or oligotypic genera, including Aligrimmia R. S. Williams, Coscinodon, Coscinodontella R. S. Williams, Indusiella, Jaffueliobryum, and Leucoperichaetium Magill. A number of segregates have been split from the large and heterogeneous Grimmia, namely Dryptodon Bridel, Guembelia Hampe, Hydrogrimmia (I. Hagen) Loeske, Orthogrimmia (Schimper) Ochyra & Zarnoweic, Schistidium, and Streptocolea I. Hagen. In this treatment, only Schistidium is accepted. Racomitrium has been divided into four sharply delimited genera and the group is recognized at the subfamily level.

R. Ochyra et al. (2003) used two peristome types to divide Grimmiaceae into two subfamilies, Grimmioideae and Racomitrioideae. The Schistidium-type peristome defines the Grimmioideae. This peristome has lanceolate teeth that are entire or perforate and distally usually split into two or three unequal prongs that are smooth to ornamented. They have a distinctly thick and trabeculate abaxial side and a thin adaxial side. There is no basal membrane . In the Racomitrium-type peristome, which defines the Racomitrioideae, the teeth are linear and divided nearly to the base into two filiform branches. The teeth are equally thickened and less prominently trabeculate on both adaxial and abaxial sides. They usually arise from a low, basal membrane and often have a prostome .[1]

Genus Schistidium

Plants (3-) 10-40(-180) mm, in dense cushions to loose mats, olivaceous , green, brown, or black, often with yellow, orange, or red tones. Leaves ovate-lanceolate, occasionally ovate-triangular, less commonly lanceolate to linear-lanceolate or elliptical to ligulate , keeled or concave proximally, sharply keeled or nearly flat distally, margins recurved, rarely plane or incurved , distal lamina usually 1-stratose or 2-stratose in striae or patches, rarely 2-stratose, specialized laminal and marginal chlorophyllose structures absent, muticous to long-awned, sometimes ending in a fleshy , multistratose apiculus ; basal cells rectangular, with straight or sinuose and thin to thick cell walls ; mid leaf and distal cells quadrate , rectangular, or ovate , rarely sub-triangular, smooth or papillose , usually sinuose and thick-walled. Gemmae absent. Sexual condition autoicous , rarely dioicous; perichaetial leaves usually enlarged. Seta short, straight. Capsule erect , immersed , symmetric , cylindric or campanulate ; annulus rudimentary or absent; operculum rostrate or rarely mamillate, usually falling attached to columella (except S. trichodon). Calyptra cucullate or mitrate, not erose, not fully covering operculum, smooth.

Species ca. 120: North America, Mexico, Central America, South America, Eurasia , Africa, Atlantic Islands, Pacific Islands, Australia, Antarctica.

The genus Schistidium has consistently fascinated yet confounded bryologists across North America. Treatments vary from region to region, and names applied to specimens at both the species and varietal levels have been as inconsistent as the characters used to differentiate the taxa. The treatment of the S. apocarpum complex by H. H. Blom (1996) and a survey of Nordic species of Schistidium (Blom 1998) assist in a better understanding of the taxonomy of this complex genus in North America, but many problems of taxonomic interpretation remain. Although Schistidium offers a great number of both gametophytic and sporophytic characters for study, some traits are not well understood and further detailed field and laboratory research is needed.

When examining a specimen of Schistidium certain steps are helpful. It is important to examine the leaves proximal to the perichaetial region. Transverse-sections from the distal region to mid leaf of multiple leaves are also critical in most cases. The necessity of numerous transverse-sections is apparent when studying S. papillosum or S. boreale, for example, as some leaves can be slightly papillose and unless numerous sections are made the papillae may be missed. Mature , empty capsules that are not overly degraded, although not always available, should be used. Transverse-sections of the capsules assist in the easier examination of the exothecial cells and peristome teeth. It is also useful to examine more than one capsule if available, as there can be some variation in exothecial cell makeup. As H. H. Blom (1996) pointed out, mixed populations are present in some sites, especially in more humid areas, so care must be taken to ensure that all species in a collection are separated. Blom also provided a great amount of supplementary detail about many of the species treated here.[2]

Taxonomy

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Notes

Name Status: Accepted Name .

Last scrutiny: 19-Jul-2004

Similar Species

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Members of the genus Schistidium

ZipcodeZoo has pages for 13 species, subspecies, varieties, forms, and cultivars in this genus:

S. agassizii (Agassiz's Schistidium Moss) · S. andreaeopsis (Schistidium Moss) · S. apocarpum (Schistidium Moss) · S. cinclidodonteum (Schistidium Moss) · S. cryptocarpum (Schistidium Moss) · S. heterophyllum (Schistidium Moss) · S. maritimum (Seaside Schistidium Moss) · S. obtusifolium (Obtuseleaf Schistidium Moss) · S. occidentale (Western Schistidium Moss) · S. pulvinatum (Pulvinate Schistidium Moss) · S. rivulare (Streamside Schistidium Moss) · S. tenerum (Schistidium Moss) · S. trichodon (Schistidium Moss)

More Info

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Further Reading

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Notes

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Contributors

Identifiers

Footnotes

  1. Roxanne I. Hastings, Ryszard Ochyra "Grimmiaceae". in Flora of North America Vol. 27 Page 39, 204, 205, 231, 265, 266, 286, 294, 306, 615. Oxford University Press. Online at EFloras.org. [back]
  2. Terry T. McIntosh "Schistidium". in Flora of North America Vol. 27 Page 204, 205, 206, 207, 218. Oxford University Press. Online at EFloras.org. [back]
Last Revised: 7/20/2012