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Published In: Species Muscorum Frondosorum 75. 1801. (Sp. Musc. Frond.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 2/17/2011)
Acceptance : Accepted
Project data     (Last Modified On 2/17/2011)

Grimmia plants are small, yellowish to blackish green and nearly always found on bare rock. The leaves are generally ovate‑lanceolate, imbricate when dry, have a strong, single costa, small, thick‑walled upper leaf cells and usually lack alar cell differentiation. Useful taxonomic features are found in the cross‑sectional shape of the leaves (keeled vs concave), leaf margins (plane, recurved, or incurved), lamina (unistratose, bi‑ or multistratose), and basal leaf cells (sinuate or straight‑walled; elongate, short rectangular or quadrate).

The Grimmia sporophyte has distinctive features that have been used to delimitate subgeneric (Loeske 1930, Jones 1933) or generic groups (Churchill 1981). Especially important characters are setae orientation (straight, flexuose, arcuate or cygneous) and capsule form (erect and symmetric vs. ventricose and asymmetric). The groups defined by these sporophytic characters appear to represent monophyletic assemblages, but nearly half the species are dioicous and rarely produce sporophytes.


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Grimmia Hedw., Sp. Musc. Frond. 75. 1801. 

Plants in dark-green or blackish green tufts or cushions, often hoary, mostly rupestral. Stems erect, forked or fastigiate branched, central strand usually present; rhizoids sparse. Leaves crowded, larger and more densely cluster at stem and branch tips, hygroscopic, imbricate, erect‑patent, crisped or spiraled, lanceolate, ovate‑lanceolate, plane, keeled or concave, gradually acute to acuminate; margins uni‑, bi‑, or multistratose, entire, plane or recurved on one or both sides; costa single, strong, subpercurrent to percurrent, flat or convex at back; upper cells mostly small and rounded‑quadrate, incrassate, often sinuose, smooth or rarely papillose, uni‑ to multistratose, basal cells quadrate, rectangular or thin‑ or thick‑walled, with straight or sinuose walls. Dioicous or autoicous. Setae short or long, straight or arcuate, twisted when dry. Capsules immersed, emergent or exserted, erect or curved, ovoid, oblong or cylindrical, smooth or ribbed when dry; stomata in neck; opercula straight or obliquely rostrate, mammillate or conic; peristome of 16 cuneiform teeth, rudimentary or absent. Calyptrae mitrate or cucullate, smooth, often lobed.


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