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Published In: Transactions of the Linnean Society of London 9: 275–282, pl. 23. 1808. (Trans. Linn. Soc. London) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

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Acceptance : Accepted
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Discussion:

Hookeria is a genus of nine species (Crosby et al. 2000), only two of which have been critically studied. The most common and well-known species, H. acutifolia, is found throughout the world. Hookeria magellanica (P. Beauv.) Arn. (Type. lherbier de M. de Jussieu, détroit de Magellan [Chile or Argentina]), however, may be the same, and it predates H. acutifolia by 20 years. Hookeria is a genus of medium-sized to large plants that have a soft, pale green color and strongly complanate-foliate stems. Unlike most other members of the Hookeriaceae, the stem of Hookeria has a rudimen-tary or weakly developed central strand. The leaves are mostly ovate and ecostate, and they have ex-tremely large, thin-walled leaf cells. Sporophytically, the genus has inclined to pendent capsules, with exostome teeth densely cross-striate on the dorsal surface and no median furrows. The endostome is typical for the Hookeriaceae: high basal membranes, stout, strongly keeled, weakly perforate seg-ments, and no cilia. Hookeria has unusually fleshy calyptrae that consist of 3–5 cell layers, with the outer 2–3 layers made up of enlarged, thin-walled, and hyaline cells.

Buck (1987, 1998) reduced the Hookeriaceae to include only Achrophyllum Vitt & Crosby, Cy-athophorella (Broth.) M. Fleisch., Cyathophorum P. Beauv., Dendrocyathophorum Dixon, Hookeria, and Schimperobryum Margad. All members of this group (except Schimperobryum and Hookeria) have single costae, but Buck (1987) considered the group unified by the presence of stem central strands, undifferentiated stem cortices, and thick-walled calyptrae. Whittemore and Allen (1989) considered the group unified only by the presence of a stem central strand, and, since they considered the presence of a central strand to be a primitive feature of the group, returned Hookeria to the bicostate/ecostate cluster of genera. A molecular study of the Hookeriales (Buck et al. 2005) re-stricted the Hookeriaceae to Hookeria and possibly Crossomitrium. These genera have ecostate leaves, but they otherwise have very little in common except generalized Hookeriaceae features.

The name Hookeria honors Sir William Jackson Hooker (1785–1865), British botanist and di-rector of the Royal Botanic Gardens, Kew, 1841–1865. Hooker was the author of Musci exotici and coauthored (with Thomas Taylor) Muscologia britanica. An indication of the importance of W. J. Hooker to botany is evident from his entry in Taxonomic Literature2 (Stafleu & Cowan 1979), which runs to 19 pages. Joseph Dalton Hooker was one of his sons.


 

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Plants medium-sized to robust, pale green or yellowish green, lustrous, in thin mats. Stems pros-trate, simple or sparsely and irregularly branched, hyaline to yellowish when young, becoming red-dish with age, complanate-foliate; stems in cross section with epidermis and cortical cells enlarged, thin-walled, central strand rudimentary to weakly developed; paraphyllia absent; pseudoparaphyllia foliose; axillary hairs 2–3 cells long, basal cell quadrate, hyaline, median cell (when present) sub-rectangular, hyaline, upper cell oblong, reddish brown; rhizoids from initials abaxial to the leaf in-sertions, reddish brown, not or sparsely and irregularly branched. Leaves not or slightly contorted when dry. Lateral leaves flattened, wide-spreading when wet, slightly asymmetric; margins entire, not or obscurely bordered by a single row of somewhat elongate and broader cells, plane; costa absent, or leaves with bistratose region at the very base; cells smooth, elongate-hexagonal to rhomboidal, laxly bulging; alar cells undifferentiated. Dorsal leaves erect, symmetric, ovate to oblong-ovate, acute or obtuse; margins plane. Asexual reproduction by reddish brown, papillose-roughened, rhizoid-like propagula, usually with straight cross-walls originating from nematogen cells at leaf apices and along or near leaf margins. Autoicous. Perigonia and perichaetia sessile along stems and branches. Setae elongate, reddish to orange, smooth, flexuose. Capsules inclined to pendent, ovoid to short-cylindric, neck moderately developed; exothecial cells collenchymatous; stomata on neck; opercula conic to conic-rostrate; annuli rudimentary, deciduous; peristome diplolepideous; exostome teeth narrowly triangular, dark red, not furrowed, densely and closely cross-striate below, coarsely papillose above, median line and trabeculae weakly developed, ventral surface smooth, trabeculae well developed and projecting; endostome as long as the exostome, yellowish white, lightly papillose throughout, basal membranes high, segments broad, strongly keeled, faintly perforate, cilia absent. Calyptrae mitrate, yellowish white, irregularly lobed at base, naked, fleshy, 3–5 cells thick, inner 2 layers small, thick-walled, reddish, outer 3 layers enlarged, thin-walled, hyaline.

 

 
 
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