Hymenostylium recurvirostrum
Hymenostylium recurvirostrum var. recurvirostrum
slender, fragile, 0.5–7 cm.
hyalodermis variably present, absent especially in depauperate plants.
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.
erect-spreading wet or dry, mostly 1–1.6(–2) mm, margins narrowly recurved proximally, rarely distally 2-stratose, base not differentiated in shape or ovate.
single, (0.04–)0.5–0.9(–1) cm.
perigonial terminal and often also lateral proximally.
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.
ca. 1–1.5 mm.
ca. (13–)17–20(–22) µm.
ca. 0.5–1 mm, usually attached to the columella at least in some capsules.
Hymenostylium recurvirostrum
Hymenostylium recurvirostrum var. recurvirostrum
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.)
Leaves of var. recurvirostrum in boreal or arctic areas are regularly strict when wet or dry, smooth and pellucid, characters previously assigned to var. commutatum, and seem to be characteristic only of depauperate morphology. Many of the leaves are deltoid; the stem hyalodermis is also absent and the sclerodermis reduced to one layer, the adaxial stereid layer reduced to only two cells. Collections may have papillae on stems, the papillae often tall (scabrous) or even taller (horrid), and such collections may be named var. scabrum or var. latifolium. This taxonomic designation would be more impressive were there some associated ecological or geographical character, which does not seem to be the case. Variety recurvirostrum is generally treated as one variable taxon throughout the flora area. S. Flowers (1973) recognized two more or less geographically distinct morphological types of var. recurvirostrum in Utah: one with a narrowly and gradually acuminate apex with a wide base with erect-patent to patent leaves, the other more abruptly acute-acuminate, more broad in the distal part of the leaf (as in var. insigne) with leaves squarrose-recurved. It is tempting to read intergradations with var. insigne of British Columbia into Flowers’s description, but every form of intergradation may be found in var. recurvirostrum, including the strongly porose leaf cells so striking in var. insigne. Variety recurvirostrum exhibits every combination of characters of var. insigne, in the thickness and porosity of the lumina, broad to narrow recurvature of the basal leaf margin(s), confined to the leaf base to recurved almost to the apex. The cells are smooth to papillose in every combination, the leaf bases flare or are narrow. Perhaps most consistent characters in var. recurvirostrum are the depauperate, that is, weakly to scarcely developed, costa and the sclerodermis of rather thickened walls in (0–)1–2(–3) rows.
(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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