Trematodon

Michaux

Fl. Bor.-Amer. 2: 289. 1803 ,

Etymology: Greek trema, hole, and odon, tooth, alluding to perforate peristome teeth
Treatment appears in FNA Volume 27. Treatment on page 437. Mentioned on page 15, 433, 434.
Leaves usually contorted when dry, lanceolate to broadly subulate from an ovate or oblong sheathing base, 1.5–4 mm, apex acute to narrowly obtuse, margins entire or with a few teeth apically; costa subpercurrect to excurrent as a subula; distal laminal cells subquadrate or short-rectangular. Perichaetial leaves distinctly larger than the cauline, convolute-sheathing. Seta elongate, 0.5–1.5 cm. Capsule long-exserted, cylindric with neck strongly differentiated, conic to long-cylindric; peristome absent or present, of 16 simple, forked or perforate teeth, vertically barred on external surface; operculum differentiated, obliquely long-rostrate. Calyptra cucullate. Spores medium-sized, 20–30 µm, papillose.

Distribution

Worldwide, mainly temperate areas.

Discussion

Species ca. 25 (6 in the flora).

Trematodon is clearly in need of revision, with more than 80 correct binomials extant but only about 25 species commonly accepted as well characterized. It clearly intergrades with Bruchia. Within the genus, only T. ambiguus and T. longicollis have strumose capsules.

Selected References

None.

Key

1 Seta short, 1-4 mm; peristome teeth undivided, annulus simple > 2
1 Seta long, (4-)10-30 mm; peristome teeth split, or perforate basally or apically, occasionally entire, annulus usually compound, revoluble > 3
2 Seta 1.5-2 mm; capsule neck short, barely as long as the urn, obovate; peristome fragile, often lost with dehiscence of operculum; leaves abruptly subulate, entire at apex. Trematodon montanus
2 Seta 1-4 mm; capsule neck slightly longer than the urn, tapering-conic; peristome persistent; leaves long-lanceolate, weakly denticulate apically. Trematodon boasii
3 Capsule neck strumose > 4
3 Capsule neck not strumose > 5
4 Capsule neck about 2-3 times the length of urn. Trematodon longicollis
4 Capsule neck about the length of the urn. Trematodon ambiguus
5 Leaves broad, ovate-lanceolate; capsule somewhat curved, peristome teeth entire or perforate near apex. Trematodon brevicollis
5 Leaves narrow, mostly long-lanceolate; capsule straight, peristome teeth perforate medially and often split near apex. Trematodon laetevirens