Plants ca. 0.5-- 2 cm ´ 1--2 mm, ascending, pale green to brownish green. Stems 0.2--0.3 mm diam., sparsely branching, transverse section with 2--3 cortical cells and 12--18 medullary cells; rhizoids numerous, colorless-pale brownish. Leaves succubous, distant to imbricate, conduplicate-concave, ovate to oblong-ovate, 0.8--1.2 ´ 0.5--0.8 mm, unequally 2--3-lobed (median lobes often absent); antical lobes subulate, more weakly arched than postical lobe, sinus between middle lobes deeper (to 0.3 of the leaf length), margins entire, apex acuminate to acute; postical lobes ovate, more strongly arched than antical lobes, sinus between middle lobes very shallow (less than 0.1 of the leaf length), margins entire, apex acuminate to acute; cells rounded-rectangular, marginal cells 8--12 ´ 10--15 m m, median cells 8--14 ´ 10--20 m m , basal cells 10--15 ´ 15--30 m m, cuticle verruculose, walls thick, trigones small; oil bodies filling the lumen, 2--8 per cell, spherical to ovoid, 2--4 ´ 4--5 m m, finely granular, grayish; underleaves absent. Specialized asexual reproduction by gemmae in masses at apices of shoots, rust-red, elliptical, 15--22 ´ 8--12 m m, 2-celled, smooth. Sexual condition dioicous. Androecia terminal, often with gemmae at tips, male bracts 4--10 pairs, similar to leaves, with antheridia, 1--2 androus, antheridial stalk 1-seriate. Gynoecia terminal, female bracts in few pairs, rounded -quadrate to broadly ovate, 3--5 lobed, equal or slightly smaller than leaves. Perianth cylindrical-obovate, 4--6-plicate, mouth ciliated with teeth 2--6 cells long. Seta 5 mm, capsule ovoid, walls 3-stratose, exterior walls with nodular thickenings, interior walls with annular thickenings, reddish brown. Elaters ca. 8 m m in diam., 2-spiral, reddish brown. Spores 9--12 m m, papillose, dark brownish.

Humic soil, humus on rocks, trunks and branches, especially Alnus and Malus in the West; 0--2000 m; Alta., B.C., N.B., Nfld., N.W.T., N.S., Ont., Que.; Alaska, Colo., Conn., Ga., Idaho, Iowa, Ky., Maine, Mass., Mich., Minn., Mont., N.H., N.Y., N.C., Ohio, S.C., Vt., Va., Wash., W.Va.; Mexico; e Africa.

In the East T. exsecta is frequently associated with Anastrophyllum minutum, A. michauxii, Bazzania trilobata, Diplophyllum apiculatum, Frullania asagrayana, Harpalejeunea ovata, Herbertus aduncus, Jamesoniella autumnalis, Lejeunea cavifolia, L. ulicina, Metzgeria crassipilis, Radula obconica, R. tenax, and Scapania nemorosa. In the West it is associated with Blepharostoma trichophyllum, Douinia ovata, Frullania nisquallensis, Scapania bolanderi, and S. umbrosa.