Cratoneuron (Sull.) Spruce

Description as per Cratoneuron filicinum:

Elements in the following description are taken from Hedenäs (2003).

Plants medium-sized, forming loose to dense interwoven mats in seepages, mostly yellow-green above and brown-green below. Stems to at least 45 mm, ascendant, subpinnately branched, beset with scattered ventral fascicles of smooth, brown rhizoids, in cross-section lacking a hyaloderm, with c. 3 layers of firm-walled cortical cells, and a weakly defined central stand; rhizoids mostly abundant, brown, smooth. Branches simple or pinnately branched, irregular in length, mostly <6 mm, occasionally to c. 15 mm. Stem and branch leaves differentiated. Stem leaves erect-spreading or weakly falcate-secund, broadly triangular, gradually narrowed to a broadly subulate and acute apex, narrowed to an auriculate and decurrent base, weakly and bluntly denticulate at basal margins, entire, crenulate or weakly toothed above in N.Z. material, weakly striate when dry, mostly 1.1-1.2 × 0.45-0.55 mm; mid laminal cells unistratose, oblong-hexagonal, mostly 21-25 × c. 6 mm, mostly 3-5:1, firm-walled, lacking pores, smooth in N.Z. material; alar cells enlarged but firm-walled, yellow-brown, abruptly differentiated and forming a large, auriculate, and decurrent group extending nearly to the costa base. Costa stout, 45-60 µm wide at base, disappearing in the subula, in cross-section convex abaxially, weakly convex adaxially, with a median band of guide cells, one adaxial and two abaxial layers of smaller (non-stereid) cells. Branch leaves smaller and narrower, ovate-lanceolate, erect-spreading, neither auriculate nor decurrent at base, mostly c. 0.5-0.75(-1.0) × 0.17-0.25 mm, weakly and rather bluntly toothed throughout; laminal cells little different from those of stem leaves; alar cells weakly inflated and firm-walled, but not forming a distinct group. Axillary hairs sparse. Paraphyllia present but sparse, foliose, broadly lanceolate, irregular, or filiform, toothed at margins, often fragmenting when removed from stem. Pseudoparaphyllia not seen, reportedly foliose.

Dioicous. Perichaetia scattered on stem, c. 0.6 mm long prior to fertilisation (mature perichaetia not seen in N.Z. material). Perigonia scattered on stems. Sporophytes not seen in N.Z. material.

Most late 20th century regional floras placed Cratoneuron in the Amblystegiaceae and included more than one species in the genus. Kanda (1976) treated four East Asian species. Crum & Anderson (1981) presented two species for eastern North America and provided an interesting commentary on the affinities of what they termed "scarcely a natural genus."

The genus is considered here to be monotypic, following its circumscription by Ochyra (1989). Ochyra’s northern hemisphere generic segregate Palustriella has had some acceptance, whereas Callialaria Ochyra has not (e.g., Smith 2004; Goffinet et al. 2009).

Kanda (1976, p.231) recorded Cratoneuron commutatum (Hedw.) G.Roth from N.Z. There are no collections of this species in N.Z. herbaria, and the record is not accepted here. This widely distributed, predominantly northern hemisphere, species is placed by some recent authors in the genus Palustriella Ochyra.