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Published In: Botanisches Centralblatt 77(2): 54. 1899. (Bot. Centralbl.) Name publication detailView in Biodiversity Heritage Library

Project Name Data (Last Modified On 2/5/2014)
Acceptance : Accepted
Project data     (Last Modified On 2/5/2014)

The Pilotrichaceae have had a complicated history, due in part to their closeness to the Hookeri-aceae and Daltoniaceae, and in part to the classic moss dilemma: conflicting systematic evidence provided by their gametophytes on one hand and sporophytes on the other. The Pilotrichaceae were originally proposed as a monogeneric family (Kindberg 1899), and later expanded to include Pilo-trichidium (Brotherus 1907c, 1925; Fleischer 1923). Miller (1971) placed 15 genera in the family on the basis of character state polarity established through the application of 23 principles for moss sys-tematics. Crosby (1974b), in a classification based principally on peristome structure, synonymized the family with the Daltoniaceae. Buck (1987, 1988) emphasized gametophytic rather than sporo-phytic characters in re-establishing the Pilotrichaceae (as Callicostaceae) for 23 genera. A molecular and morphological analysis of the group (Buck et al. 2005) more or less supported the generic make-up of Callicostaceae, and placed Pilotrichum in its own subfamily.

The Pilotrichaceae are treated here as a monogeneric family that occupies a transitional position between the families traditionally placed in the Hookeriales and the Leucodontales. The uniqueness of the Pilotrichaceae is supported by the following constellation of characters that seems to span the Hookeriales-Leucodontales families: creeping, sympodially branched stolons; weakly and irregularly branched rhizoids from clusters of initials abaxial to the stolon leaf insertions; filamentous to subfo-liose pseudoparaphyllia; stipitate-frondose habit; stems with a hyalodermis but no central strand; 2-celled axillary hairs; leaf cells small, thick-walled, often unipapillose; alar cells absent or weakly dif-ferentiated; costae double, long, strong, often with a dorsal crest and with dorsal propagula; setae short; exothecial cells thick-walled; peristome with narrow, completely papillose exostome teeth; en-dostome segments flat, cilia absent or rudimentary; calyptrae mitrate and having archegonia remnants as well as multiseriate hairs.

Buck (1987, 1998) viewed the most morphologically reduced members of Pilotrichum as the basal members of the genus. On the basis of this interpretation, he considered Pilotrichum phyloge-netically close to Callicostella. The opposite view is taken here, and the morphologically complex species, especially those with well-developed stolons and stipitate-frondose habit, are considered the basal members of the genus, thus relating the group to the Leucodontales.


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 Plants medium-sized to large, sometimes slender and wiry. Stolons creeping; rhizoids from clus-ters of initials abaxial to the leaf insertions, on stolons, and at the base of primary stems. Stems erect to pendent, typically stipitate, regularly pinnately to bipinnately branched; branches determinate or indeterminate, evenly foliate; stems in cross section with a well-developed sclerodermis (sometimes with a unistratose hyalodermis), central strand absent; paraphyllia absent; pseudoparaphyllia nar-rowly foliose to filamentous; axillary hairs 2-celled. Stipe leaves appressed or appressed below and squarrose above; margins often narrowly recurved. Stem and branch leaves smooth or undulate to ru-gose, decurrent; margins subentire, serrulate, or serrate, plane, recurved or inflexed, at times bordered by elongate to sigmoid cells; costae strong, double, reaching above midleaf, often subpercurrent, par-allel or diverging throughout, at times with a dorsal crest, usually ending in a stout tooth, in cross sec-tion with homogeneous, thick-walled cells; cells short, thick-walled, smooth or prorate, occasionally porose; alar cells not or weakly differentiated. Asexual propagula often present on costae or leaf mar-gins. Dioicous, synoicous, or autoicous. Setae short, flexuose, smooth or roughened above. Capsules exserted or immersed, erect, oblong-cylindric, symmetric; exothecial cells thick-walled; stomata usu-ally present; opercula short-rostrate; annuli rudimentary; peristome diplolepideous; exostome teeth pale yellow, narrowly triangular, dorsal (outer) surface papillose throughout, trabeculae and median line faint; endostome yellow, lightly papillose throughout, basal membranes low, segments not or nar-rowly perforate, not keeled, cilia rudimentary or absent. Calyptrae mitrate, with archegonia and/or sparse hairs.


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