Tortella humilis (Hedw.) Jenn.

Plants usually dull and dark green to sordid yellow-green distally, brown to black proximally, typically compact and rosulate to more elongate and showing annual whorls. Stems almost absent or stems to 0.5(-0.7) cm, central strand distinct, densely radiculose with red-brown radicles or infrequently populations with elongate stems without tomentum. Stem leaves densely foliose in rosulate habits, abruptly larger distally, the whorl-bases consisting of small leaves, loosely and variously incurled and contorted, occasionally somewhat crisped when dry, widespreading to patent when moist, typically oblong or oblong-spathulate, most leaves flat at mid leaf, somewhat concave and weakly keeled near the apex, not cucullate; 1.5-3.5(-4) mm; base sub-clasping and often appearing narrower than the limb to somewhat broader and elliptic; margins flat to weakly and broadly undulate, erect or broadly incurved near the apex; apex typically obtuse to broadly or occasionally narrowly acute, usually stoutly mucronate; costa short-excurrent, adaxial surface papillose, adaxial epidermal cells typically quadrate to short-rectangular and similar to the laminal cells throughout, sometimes smooth and narrowly elongate cells (8:1) toward the apex due to exposure of the stereid band or, in the extreme apex, exposure of the guide cells; in cross section adaxial epidermis present, often interrupted in the extreme distal portion of the leaf, proximal laminal cells yellow-hyaline, elongate, laxly thin-walled, gradually distally papillose, marginal basal cells longer and larger than median cells, occasionally approximating a band of differentiated cells; proximal cells interior to the marginal gradually differentiated from the distal laminal cells; distal laminal cells small, typically 6-7(-9) µm wide. Specialized asexual reproduction none. Sexual condition autoicous; perigonia small, distinctive, stalked, flattened, usually single, rarely geminate, frequently yellow or orange, foliose buds of 2-6 leaves in axils of the distal leaves alongside and proximal to the perichaetium; inner perichaetial leaves little differentiated from stem leaves. Seta about (0.5-)0.7-1.7 cm; one per perichaetium, but often three to four per plant from different branches. Capsule 1.5-3 mm; annulus deciduous in fragments; operculum 1.2-1.5 mm; peristome teeth, to over 1 mm, spirally wound 2 or 3 times.