Calliergon (Sull.) Kindb.

Plants mostly robust, green to brown-green, in wet habitats and often emergent. Stems elongate, ascendant and self-supporting or decumbent, scarcely to densely and irregularly branched, rarely regularly pinnate, in cross-section lacking a hyaloderm and with a weak central strand. Stem leaves ± spreading or erect-imbricate, never secund, crowded or remote, larger than branch leaves, concave, broadly ovate or oblong, rounded or obtuse and often cucullate at apex, entire, smooth or striolate when dry, not bordered, ± plane at margins, mostly weakly decurrent, sometimes producing abaxial rhizoids near apex; mid and upper laminal cells unistratose, linear, ± flexuose, often weakly porose, smooth, shorter in extreme apex, becoming narrower and longer near margin but not forming a distinct border, sometimes with differentiated rhizoid initials which are broader and less chlorophyllose than adjacent cells near apex; alar cells thin-walled, inflated, ± hyaline, forming a large triangular to broadly ovate and ± decurrent group which is abruptly or gradually differentiated from the adjacent laminal cells. Costa strong, single, unbranched or forked above, to mid leaf or nearly to the leaf apex. Branches usually ± cuspidate apically because of crowded leaves. Branch leaves smaller and narrower than stem leaves, broadly rounded to acute at apex. Pseudoparaphyllia present, foliose. Paraphyllia absent.

Autoicous or dioicous. Setae very long and slender, red or straw-coloured; capsules oblong-cylindric, curved and inclined; exothecial cells firm-walled and oblong; stomata as for family; annulus apparently none. Peristome hypnoid, as per family, with endostomal cilia in groups of 2 or 3 and nodose. Spores finely papillose.

A narrow view of Calliergon, following the interpretation of the genus and its allies by Hedenäs (1993), is presented here. According with this restricted view of the genus, only a single species, C. richardsonii, occurs in N.Z.

Two other species which are included in Calliergon in some modern Floras are here treated in other genera. The species treated as Acrocladium sarmentosum by Sainsbury (1955, p. 435) (but sometimes known as Calliergon sarmentosum) is here treated in the genus Warnstorfia. The species treated here as Straminergon stramineum was not treated by Sainsbury (1955), but is included in Calliergon in some modern Floras.

A broader interpretation of Calliergon is made by Kanda (1976, 1977) in his treatment for Japan. A world-scale monograph of Calliergon was presented by Karczmarz (1971). Karczmarz’s treatment employs very narrow specific and infra-specific taxonomic concepts and is very difficult to use; his concepts are not applied here.

According to Hedenäs (2003, p. 456) axillary hairs in Warnstorfia are abundant, with 1–2 short brown basal cells and mostly 2–8 elongate and hyaline upper cells.

The following key will separate the three N.Z. species included in Calliergon by Brotherus (1925).

Calliergon cordifolium (Hedw.) Kindb. was recorded from N.Z. by Brotherus (1925, p. 348). The source of this record is almost certainly the W. Bell collection from Diamond Lake (annotated by Brotherus as C. cordifolium) which is referred below to C. richardsonii.

Calliergon giganteum (Schimp.) Kindb. Hedenäs (pers. comm., 23 July 1996) named a single, non-localised N.Z. specimen in the Stockholm herbarium (S) as this widespread northern hemisphere species. The collector (R. v. Bahr) of this collection is unknown to me. Calliergon giganteum has longer costae than C. richardsonii and is dioicous; the occurrence of C. giganteum in N.Z. is doubtful.

Calliergon laxirete Zanten & J.K.Bartlett is a synonym of Bryum blandum, as first recognised by Beever (1992).