Hymenostylium recurvirostrum
Hymenostylium
hymenostylium moss
slender, fragile, 0.5–7 cm.
0.5–7(–10) cm, often sparingly branched by subfloral innovations, smooth or occasionally scabrous-papillose;
transverse section round, rounded-pentagonal, or triangular, hyalodermis usually absent, sclerodermis present, central strand absent [present];
moderately radiculose proximally, occasionally to the apex;
axillary hairs of around 8 cells, the basal 1–2 cells brownish or occasionally all cells hyaline.
more or less distant;
costa ending 1–2 cells before apex to percurrent or short-excurrent as a flat to conical apiculus, occasionally ending in a pellucid cell, often scalloped along margins by projecting cell walls, at mid leaf with 2–4 or occasionally several rows of cells across adaxial surface;
costa adaxial surface are U-shaped in section;
basal cells gradually differentiated, elongate-rectangular, less to nonpapillose proximally, larger than distal cells, 20-50 µm, 2–4:1, walls firm, narrower on the margins, pellucid;
distal laminal cells heterogeneous: subquadrate to short-rectangular or rhomboidal, with occasional diagonally transverse walls, longitudinally elongate especially distally near the costa, walls commonly irregularly thickened to porose, marginal cells smaller and more quadrate, ca. 7–10(–12) µm wide, 1–3:1, 1:2, seldom 2-stratose in patches, cell walls superficially flat to somewhat convex, firm-walled;
papillae low, simple to 2-fid, 1–3(–5) per lumen, dense to scattered, occasionally absent.
appressed to appressed-incurved and weakly contorted when dry, weakly to strongly spreading-recurved when moist;
linear- to oblong-lanceolate, adaxial surface sharply keeled or canaliculate, 0.5–2.8(–3) mm;
base scarcely differentiated to ovate or rectangular, sometimes semi-sheathing proximal to a reflexed distal lamina;
distal margins narrowly recurved along 1 or both sides, or margins of expanded base broadly recurved, all margins papillose-denticulate to smooth or scalloped-denticulate, occasionally 2-stratose distally in small to extensive patches, apex sharply to bluntly acute, sometimes apiculate with a clear cell, acuminate-mucronate, or rarely obtuse to rounded;
costa ending 2–6 cells before the apex or percurrent to excurrent as a stout mucro, costal adaxial cells epapillose, in 4–5 rows, abaxial cells elongate, 3:1, papillose or smooth, transverse section semi-circular or concave adaxially, adaxial costal epidermis absent, adaxial stereid band present but absent in depauperate plants, guide cells 2–4(–6) in one layer, hydroid strand absent, abaxial stereid band well developed, abaxial epidermis absent or weakly differentiated;
basal cells differentiated, typically firm to occasionally lax medially, rectangular, 2–4:1, even or often strongly irregularly porose, with narrower rectangular cells extending into a slender, often fragile decurrency;
distal laminal cells typically heterogeneous, larger along the costa grading to distinctly smaller on the margins, irregularly subquadrate to short-rectangular to porose throughout, 8–12 µm wide, 1–2(–3):1, cell walls thin to typically incrassate, flat to slightly convex in section, papillae simple and sharp to 2-fid, 1–3 or more per lumen, centered to scattered, occasionally absent, lumina clear to pellucid.
single, (0.04–)0.5–0.9(–1) cm.
yellow when young, red-brown with age, 0.5–1 cm, twisted clockwise.
perigonial terminal and often also lateral proximally.
dioicous;
perigonia gemmate, terminal;
perichaetia terminal, leaves little different from the cauline, somewhat longer, slightly sheathing.
urn 0.5–0.9(–10) mm, often widest at the mouth when dry, exothecial cells thin- to thick-walled, 1–4:1, stomates phaneropore at base of capsule;
annulus weakly vesiculose.
yellow to red-brown, variably globose, ovoid, obovoid, or subcylindric, ca. 0.5–1 mm;
operculum inconstantly systylius, obliquely conic-rostrate, 0.2–1 mm;
peristome absent.
ca. 1–1.5 mm.
cucullate, smooth.
ca. (13–)17–20(–22) µm.
ca. 17 µm, brownish, finely papillose.
ca. 0.5–1 mm, usually attached to the columella at least in some capsules.
asexual reproduction none.
laminal color reaction yellow.
Hymenostylium recurvirostrum
Hymenostylium
Varieties 5 (2 in the flora).
Hymenostylium recurvirostrum is distinctive among similar species in having one laminal margin typically recurved, the other erect. A character often overlooked in texts is the universal presence of a long, narrow, fragile decurrency in the basal angles. Both Gymnostomum aeruginosum and Eucladium verticillatum have an adaxial epidermis in the costal section, with papillose and quadrate cells on the adaxial surface of the costa in plane view, and the costa profile is round (convex), but Hymenostylium has long, thin and smooth cells in plane view because the epidermal layer is not developed, and the costal profile is convex adaxially, being lunate in section. In Anoectangium aestivum, as in those two species, the dense laminal papillae often obscure cell lumens, but the leaf section shows a very deeply keeled leaf with the leaf lamina adjacent to the costa nearly contiguous or touching, showing a deep, narrow channel in plane view and a circular costa section. The adaxial stereid band is always absent in A. aestivum, but often present in H. recurvirostrum. Molendoa sendtneriana is similar but has a stem central strand, and lateral perichaetia (like A. aestivum).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Species 15 (1 in the flora).
Aside from the gymnostomous capsule, the most important character distinguishing Hymenostylium from other genera in the flora area is the absence of a stem central strand. Gymnostomum, with a similar habitat, has a central strand. Species in the peristomate genus Hennediella, for example, also may have systylius capsules but have central strands in addition to a laminal marginal border, while the costal adaxial stereid band is absent. The genus Trichostomum has a stem central strand, as is characteristic of Barbula and Didymodon. Leptodontium is similarly without a stem central strand, has a strong sclerodermis and hyalodermis, and reduced costa in cross section, but is distinct by the well-developed peristome, toothed leaf margin and nonhygric habitat. Eucladium, also without a central strand, lacks a sclerodermis, and its costa has both an ab- and adaxial epidermis and two stereid bands. Hymenostylium is frequently if perhaps not accurately described and illustrated as having no hyalodermis. However, a large hyalodermis was often present in specimens from the flora area, this usually collapsed and perhaps overlooked. According to R. H. Zander (1993), Hymenostylium is phylogenetically related to Leptodontium in the Leptodontieae, whereas Gymnostomum, a genus into which Hymenostylium is often placed, belongs with the Barbuleae.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaves 1-1.6 mm, margins narrowly recurved proximally, rarely 2-stratose distally, base not differentiated in shape or ovate; stem hyalodermis variably absent or present, leaf cells mostly evenly thickened except along the costa; costa in section depauperate, adaxial stereids (0-)2-4 cells across, stem sclerodermis of (0-)1-2(-3) layers | var. recurvirostrum |
1. Leaves (1.6-)2-2.4 mm, margins broadly recurved proximally, often 2-stratose in patches distally, base rectangular, flaring, with shoulders; stem hyalodermis always present, leaf cells distinctly porose throughout or at the leaf base, especially along the costa; costa in section robust, adaxial stereids 6-8(-10) cells across; stem sclerodermis thick, of 3-5 layers | var. insigne |
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