BFNA Title: Hookeriaceae
Author: P. M. Eckel
Date: March 16, 2010
Edit Level: R
Version: 1

Bryophyte Flora of North America, Provisional Publication
Missouri Botanical Garden

BFNA Web site:


Return to Home



Patricia M. Eckel

Plants medium to large, creeping, in mats or patches. Stems green, hyalodermis and sclerodermis absent, stem central strand present. Leaves loosely complanate-foliate, broad, apices flat, rounded-obtuse to sharply or broadly acute, often asymmetric and somewhat dimorphic with dorsal leaves broader and more symmetric than lateral leaves, margins unbordered, entire, plane; laminal cells large, lax, smooth, uniform across the insertion and leaf base or somewhat shorter than the medial; costa completely absent. Specialized asexual reproduction by unbranched, uniseriate, subpapillose filaments among apical leaf rhizoids. Sexual condition autoicous [dioicous]. Seta red to reddish or blackish brown, elongate, smooth. Capsule suberect to pendulous, smooth, ovoid to cylindric; annulus distinct in one to several rows of cells; exothecial cells strongly collenchymatous; operculum conic-rostrate; peristome dark red, diplolepideous; exostome unfurrowed, with a zigzag median line; endostome basal membrane high, processes more or less perforate, extending just beyond the exostome teeth, cilia rudimentary or absent. Calyptra mitriform, multistratose at middle, smooth, naked, somewhat lobed at the base.


Genera 2, species ca. 8 (1 genus, 2 species in the flora): worldwide in tropical and temperate regions.


The Hookeriaceae, once of many genera (W. H. Welch 1966, 1976), is recently recognized as comprised of two genera (B. Goffinet et al. 2008; W. Frey 2009): Crossomitrium, with 6 species (B. H. Allen 1990), and Hookeria with 10, only two of which are well known (M. R. Crosby et al., Checklist of the Mosses, unpublished, 1999). The absolute absence of a costa in the leaves is a major character separating this family from closely related families.


Crossomitrium, a neotropical South American endemic genus, is absent in the floral area. Although considered to be in the same family, the striking characteristics as detailed by B. H. Allen 1990) of Crossomitrium separate it from Hookeria including traits of stem, leaf apices and margins, sexuality, seta ornamentation, exothecial cell walls, peristome color, ornamentation of calyptra, type of asexual reproduction, and habitat. Also, the stem cross section of Crossomitrium has a moderate scleroderm with larger, thinner cortical cells toward the stem center. In Hookeria the section shows no epidermal differentiation, the cells are large and lax throughout, and they are also heteromorphic with smaller cells interspersed throughout the central cylinder before the abrupt and large central strand, composed of very small cells that appear to be somewhat colored. The two species of Hookeria in the flora have laminal cells observable with a hand lens, being large, lax and broadly oblong-hexagonal or rhomboidal. However, the cells of Crossomitrium species are all long-linear to vermicular with comparatively thicker walls.


SELECTED REFERENCES  Allen, B. H. 1990. A revision of the Genus Crossomitrium (Musci: Hookeriaceae). Tropical Bryology 2:3--34.  Frey, W., ed. 2009. Syllabus of Plant Families: A. Engler's Syllabus der Pflanzenfamilien. Part 3. Bryophytes and seedless Vascular Plants. Berlin.  Goffinet, B., W. R. Buck and A. J. Shaw. 2008. Morphology, Anatomy, and Classification of the Bryophyta. In: B. Goffinet and A. J. Shaw, eds. Bryophyte Biology, ed. 2. Cambridge, pp. 55--138. Welch, W. H. 1966. The Hookeriaceae of Mexico. Bryologist 69: 1--68.  Welch, W. H. 1976. Hookeriaceae. North American Flora, series 2, part 9: 1--120.


1. HOOKERIA Smith, conserved name. Trans. Linn. Soc. London 9: 275. 1808 * [For William Jackson Hooker, 1785--1865, British bryologist and Director, Kew Gardens]


Plants prostrate, dorsal and ventral surfaces distinct relative to the ground, soft, flaccid, varnished-shiny in incident light, appearing matt to the naked eye, in loosely foliate whitish to light green or pale yellowish mats, somewhat contorted when dry, sparsely and irregularly branched; paraphyllia absent, pseudoparaphyllia reportedly filamentous or absent; rhizoids sparse, unbranched, hyaline to brown. Stems 1--5(--7.5) cm, fleshy and succulent, cortical cells in section large, concolorous, heterogenous throughout, lacking a differentiated epidermis and sclerodermis, central strand distinct, of markedly smaller, somewhat colored cells. Axillary hairs hyaline, 2--4-celled. Leaves  2--4.5(--6) mm, often radiculose at the leaf tips with occasional filamentous gemmae, ovate, oblong-ovate, elliptic to broadly lanceolate; apex rounded-obtuse to bluntly to broadly or sharply acute; base somewhat decurrent at the margins; margins plane, entire, borderless, with elongate cells, evenly thickened or slightly narrower in a single marginal row; laminal cells 100--200(--250) \um, broadly oblong-hexagonal or oblong-rhomboidal to shortly rectangular, becoming smaller in all dimensions toward the apex or narrower on the margins, sometimes heteromorphic with smaller cell-pairs scattered throughout the leaf, thin-walled, pellucid. Sexual condition autoicous and apparently dioicous. Seta stout, flexuose-curved, (0.8--)1--2(--2.5) cm. Capsules oblong-cylindric or ellipsoid, 1.5--2 mm, neck short, containing phaneropore stomata; operculum long-rostrate from a conic base; annulus of 1--2 rows of large cells, weakly deciduous; exothecial cells strongly collenchymatous, subvesiculose; exostome teeth dark red and cross-striolate basally, pale and papillose distally, bordered and trabeculate; endostome pale, finely papillose, segments narrowly open on the keel. Calyptra shortly conic-mitrate, 2--2.5 mm. Spores small, (10--)12--17 \um, spheric, smooth to scarcely or minutely papillose.


Species 2(--8): e,w North America, Central America, n South America, Eurasia, Africa, Atlantic Islands, Pacific Islands.


Absence of a costa, complete lack of a border, and very large leaf cells observable with a hand lens readily separate species of Hookeria from other pleurocarpous mosses in the floral area. The glossy, “lucent” or iridescent quality of the plants is associated with the cell walls exhibiting a varnished appearance in incident light under a microscope. The large lumina, however, render a dull or matt appearance to the naked eye. When moistened, the plants appear almost transparent, or pellucid. Paraphyllia and pseudoparaphyllia are absent in Crossomitrium (B. H. Allen 1990), but according to B. Goffinet et al. (2008), pseudoparaphyllia in the family are filamentous or absent; perhaps this applies only to the genus Hookeria. One species of Hookeria has a tropical distribution, but also occurs in the temperate zone, the other is a north temperate species of both the New and Old Worlds.



1. Leaves acute, laminal cells (except rhizoid initials at the apex) more or less homogenous; capsules not or little contracted below the mouth when dry; elongate marginal laminal cells in a single row, narrower than median cells……………………..........................1. Hookeria acutifolia


1. Leaves obtuse, laminal cells with scattered pairs of smaller cells, one smaller relative to the other and quadrate, resembling the rhizoid initials at the apex; capsules strongly contracted below the mouth when dry; elongate marginal laminal cells equal in width to median cells   .................... 2. Hookeria lucens


1. Hookeria acutifolia Hooker & Greville, Edinburgh J. Sci. 2: 225. 1825


Pterygophyllum acutifolium (Hooker & Greville) Müller Hal., Linnaea 21: 194. 1841; Hookeria? sullivantii Müller Hal. in Lesquereux & James


Leaves acute, laminal cells (except rhizoid initials at the apex) more or less homogenous; elongate marginal cells in a single row, narrower than median cells. Capsules not or little contracted below the mouth when dry.


Capsules mature late fall--spring. Steep to vertical banks to crevices and recesses in cold streams, gullies, ravines, mouths of caves, ledges and under overhanging cliffs, deep shade of evergreens and mixed hardwood forests, by waterfalls, gneiss, shale, conglomerates but mostly on sandstone, in coves, low cloud forests, occasionally with Bryoxiphium, Trichomanes, Vittaria spp.; 550--2500 m; B.C.; Ala., Ark., Conn., Ga., Ill., Ind., Ky., N.C., Ohio, Pa., S.C., Tenn., Va., Wash., W.Va.; Mexico; Central America; West Indies; N.C. South America; e Asia; Africa; Pacific Islands (Hawaii).


 Hookeria acutifolia is a species of warm-temperate and tropical distribution, being rare and scattered in eastern North America, and disjunct to British Columbia and Washington states.      The leaves may be somewhat more lanceolate (broadest below the middle) than those of H. lucens. The cells are smaller than the medial in the apex where rhizoids appear to initiate. This species is seldom fruiting but capsules and vegetative propagula were reported by E. Lawton (1971) from Washington State. The only specimen of fruiting material of H. acutifolia seen in the study area was a collection from British Columbia, Queen Charlotte Islands (Bryophyta Canadensia (Schofield & Boas 18735), but were old and too broken and distorted to describe, and had clearly fruited well before July 9--12. The oceanic habitat appears conducive to fruiting in this species.


When the leaf apex lacks rhizoids, the apex is sharply acute and tipped with a small sharp apical cell, but when rhizoids are present, the apical cells are digested and the apex becomes erose and bluntly rounded-acute, but never smoothly rounded-obtuse as in H. lucens.  Hookeria acutifolia was reported as autoicous in the moss flora of Mexico (F. D. Bowers 1994), in eastern North America (H. A. Crum and L. E. Anderson 1981), England (A. J. E. Smith 1978) and China (Lin Bang-juan and B. C. Tan 2002). However, E. Lawton (1971) described specimens from the Pacific Northwest as having perichaetia and gemmiform perigonia on separate plants---a dioicous condition that needs to be explored.



2. Hookeria lucens (Hedwig) Smith, Trans. Linn. Soc. London 9: 275. 1808


Hypnum lucens Hedwig, Sp. Musc. Frond., 243. 1801


Leaves obtuse, laminal cells with scattered pairs of smaller cells, one smaller relative to the other and quadrate, resembling the rhizoid initials at the apex; elongate marginal laminal cells equal to width of median cells. Capsules strongly contracted below the mouth when dry.


Capsules mature late fall--spring. Coastal islands and adjacent mainland, ravines, pools near rivers, swampy lake margins, raised bogs in peaty muck, wet evergreen woods of Tsuga, Chamaecyparis, Alnus, forests of Sequoia sempervirens, coastal Sitka spruce forests, old logs in heathland; 0--500 m; B.C.; Alaska, Calif., Idaho, Oreg., Wash.; Europe; Asia (Caucasus, Turkey); Atlantic Islands (Faeroe Islands, Madeira Islands).


A. J. E. Smith (2004) reported that in England the capsules of Hookeria lucens mature in late autumn to spring. Also, in England, uniseriate chlorophyllous caducous filaments are occasionally produced from small cells in the distal portion of the leaf (A. J. E. Smith 2004) but such vegetative propagules were not seen in specimens examined for the flora.



Bang-juan, Lin and B. C. Tan 2002. Hookeriaceae. In:  Si He, ed. Moss Flora of China Hookeriaceae--Thuidiaceae.  Vol, 6.  Beijing and St. Louis, pp. 3--34).

Bowers, F. D. 1994. Hookeria  In: The Moss Flora of Mexico, A. J. Sharp,  H. A. Crum and P. M. Eckel, eds. Mem. New York Bot. Gard. 69. 2 Vols., pp. 780--781.

Crum, H. A. and L. E. Anderson. 1981. Mosses of Eastern North America. 2 Vols. New York.

Lawton, E. 1971. Moss Flora of the Pacific Northwest. Hattori Botanical Laboratory, Japan.

Smith, A. J. E. 2004. The Moss Flora of Britain and Ireland, ed. 2. Cambridge.