XX. GYROTHYRACEAE R. M. Schuster
Plants prostrate, mat-forming; branches infrequent (except below perianth), lateral intercalary from axils of leaves; without flagella. Leaves alternate, succubous, plane, simple, entire; Underleaves large, 2-lobed. Rhizoids abundant, confined to periphery of regularly spaced, reddish purple, cushion-shaped pads on ventral side of the stem. Asexual reproduction by unicellular gemmae occasional. Gynoecium terminal. Perianth reduced, hidden in bracts, perigynium (coelocaule) present, forming a short incipient marsupium. Capsule wall 2-stratose, without secondary thickenings; 4-valved, with the valves spirally twisted.
Genera 1, species 1: endemic to the coastal area of the Pacific Northwest, from Alaska to northern California.
The monotypic Gyrothyraceae is a family of the suborder Jungermanniineae. In a phylogenetic analysis of this suborder (Shaw et al. 2015), the family is resolved as most closely related to the now recognized monogeneric families Harpanthaceae and Arnelliaceae. Reduced perianths and short marsupiate perigynia characterize all 3 families, but only Gyrothyraceae possess regularly spaced ventral rhizoid cushions, and long, spirally twisted capsule valves.
SELECTED REFERENCES Crandall-Stotler, B., R. E. Stotler & D. G. Long. 2009. Phylogeny and classification of the Marchantiophyta. Edinburgh J. Bot. 66: 155--198. Schuster, R. M. 1955. Notes on Nearctic Hepaticae. IX. The relationships of the genus Gyrothyra. Bryologist 58. 137--141. Schuster, R. M. 1970. Studies on Hepaticae XVIII. The family Jungermanniaceae, s. lat.: a reclassification. Trans. British Bryol. Soc. 6: 86--107. Shaw, B. et al. 2015. Phylogenetic relationships and morphological evolution in a major clade of leafy liverworts (Phylum Marchantiophyta, Order Jungermanniales): Jungermanniineae. Syst. Bot. 40: 27--45.
1. GYROTHYRA M. A. Howe, Bull. Torrey Bot. Club 24: 201. 1897 * [Greek, gyro, twisted, and thyra, door, alluding to spirally twisted capsule valves]
Plants of medium size, somewhat dorsiventrally flattened. Stems fleshy, little branched, with all branches of the Plagiochila-type, with collars 1-stratose and tightly appressed to the branch base. Leaves without secondary pigmentation, imbricate, horizontal to patent, orbicular to ovate (lingulate), with the apex rounded; cells of the margin slightly inflated, forming a border; interior cells thin-walled with conspicuous triangular to slightly bulging trigones; 2--5 ellipsoidal oil bodies in all cells. Underleaves reddish purple, rectangular. Gemmae formed on flagelliform apices of senescent male shoots. Sexual condition, dioicous, with male plants more slender than females. Androecia intercalary on leading stems, with up to 6 antheridia per bract. Gynoecia subtended by1--2 subfloral innovations; bracts and bracteoles in 2--3 series; perianth hyaline, tubular, only the constricted mouth emerging from the bracts, subtended by a well-developed fleshy, incipient marsupium. Sporophyte seta large, unspecialized. Capsule dark brown, ellipsoidal; capsule wall bistratose, without secondary wall thickenings; elaters free, with 2(--3) dark-brown spiral thickening bands; spores brown, spheroidal, apolar, with the wall minutely papillate.
Species 1 (1 in the flora): endemic to the Pacific Northwest.
In dorsal aspect and habit, Gyrothyra resembles a Jungermannia or Nardia, but is easily distinguished from both by its 2-fid underleaves, unique purple rhizoid pads, and elongate, spirally twisted, 2-stratose capsule valves. The genus was aligned with Isotachis by T. C. Frye and L. Clark (1943) and R. M. Schuster (1972) because of its spiral-valve dehiscence pattern, but its gynoecial organization is like that of many lineages in the Jungermanniineae, and is in accord with its molecular phylogenetic placement as sister to Harpanthus (A. J. Shaw et al. 2015). The reddish purple rhizoid pads or cushions that reside at the base of every underleaf are a unique diagnostic feature that occurs in no other taxon of hepatics.
SELECTED REFERENCES Crandall-Stotler, B. 1976. Anatomy and development of the sporophyte of Gyrothyra underwoodiana Howe. J. Hattori Bot. Lab. 40: 355--369. Crandall-Stotler, B. 1977. Morphogenesis and anatomy of the gametophyte phase of Gyrothyra underwoodiana Howe. Nova Hedwigia 29: 257--279. Frye, T. C. and L. Clark. 1943. Hepaticae of North America, Part II. University of Washington Publications in Biology 6: 163--334. Schuster, R. M. 1972 . Phylogenetic and taxonomic studies on Jungermanniidae. J. Hattori Bot. Lab. 36: 321--405.
1. Gyrothyra underwoodiana M. Howe, Bull. Torrey Bot. Club 24: 202. 1897 E
Plants 10--20 × 2--4 mm, forming light green mats over shaded soil. Stems dorsally flattened, 400--650 /um wide; in transverse section, cells thin-walled, with epidermal cells 32--40 /um gradating to larger inner cells, 40--64 /um; cells of the ventral surface reddish purple, narrowly rectangular, 5--80 × 6--8 wide, forming oval pads basal to each underleaf insertion; rhizoids abundant, arising from the periphery of the pads, hyaline to yellowish brown. Leaves 1--2.2(--4.0) x 1--2 mm, with those on female plants longer than those on male plants; marginal cells quadrate to short rectangular, 40--48 x 32--40 /um; interior cells isodiametric to slightly elongate, ca. 32--48 /um; cells at dorsal base larger, 64--70 x 48--52 /um; cell surface finely granulate; oil bodies coarsely granulose, grey to grey-brown. Underleaves transverse, planate, 0.6--1 x 0.25--0.30 mm, 2-fid to 2/3 length, margins entire; lobes subulate, unequal in length and width, erect to divergent, with the apices 1-seriate and the sinus acute; cells evenly thin-walled, rectangular, 60--80 x 25--32 /um, trigones small, with the cell surface granulate; oil bodies as in the leaf cells. Gemmae green, spheroidal, unicellular, 10--24 /um. Androecia with 3--6 pairs of bracts and 3 unmodified bracteoles; bracts smaller than vegetative leaves, orbicular, erect to sub-erect, slightly enrolled dorsally, reddish purple basally; antheridia ovoid to pyriform, yellow at maturity, with the stalk short. Gynoecia with the coelocaule oriented at right angles to the stem, forming a short, fleshy marsupium around the sporophyte foot, seta and lower part of the capsule, reddish purple, dorsally concealed by the bracts inserted on it, 3--4 x1--1.5 mm wide, 10--20 cell layers thick; with rhizoids only near bract insertions. Sporophyte foot large, with a well-developed involucellum or collar. Seta up to 12 cells in diameter. Capsule up to 2 x 0.8 mm, with valves apically free; capsule wall with cells of both layers, rectangular, with equally thickened brown walls; elaters 200--450 x12--15 /um; spores 12--15 /um.
On shaded, moist bare soil, along roadsides, trails, or on damp rocks along small streams; low to moderate elevation; B.C.; Alaska, Calif., Oreg., Wash.