• Corpus ID: 82945618

Austral Hepaticae 37. The sporophyte of Megalembidium Schust., together with a re-evaluation of the taxonomic position of the genus

@article{Braggins2005AustralH3,
  title={Austral Hepaticae 37. The sporophyte of Megalembidium Schust., together with a re-evaluation of the taxonomic position of the genus},
  author={John E. Braggins and John J. Engel},
  journal={Journal of The Hattori Botanical Laboratory},
  year={2005},
  pages={81-96}
}

• J. Braggins, J. Engel
• Published 2005
• Biology
• Journal of The Hattori Botanical Laboratory

Current classification of the New Zealand hepatic Megalembidium insulanum (Mart. & Hodgs.) Schust. in Lepidoziaceae and in subfamily Lepidozioideae is discussed. Recent discovery of the gynoecium and sporophyte, together with detailed studies of the androecium, show that Megalembidium is beyond the circumscription of subfamily Lepidozioideae. The genus is placed in a new subfamily, subfam. Megalembidioideae. Affinities of subfam. Megalembidioideae and subfam. Lembidioideae, particularly fsolembidium, are discussed. Megalembidium insulanum (Mart. & Hodgs.) Schust., the only spec ies comprising the genus Megalembidium (Lepidoziaceae), has an interesting history, all of it unfolding within the last half century. The species was initially described as a Lembidium by Martin and Hodgson (Martin, 1950) for a plant collected by Martin at Pegasus Creek, Stewart Island. Two to three months later (see Schuster, 1980, p. 399), Herzog (1952) described Dendrolembidium marfinii Herz. based upon a specimen collected by Martin from Table Hill , Stewart Island that was sent to him by Mrs. E. A. Hodgson. Herzog (1952) included three spec ies in the genus Dendrolembidium Herz. , D. tenax (Grev.) Herz., D. dendroides (Carring. & Pears.) Herz. and D. martinii; Allison and Hodgson (Allison, 1960) added a fourth spec ies by transferring Lembidium insulanum Mart. & Hodgs. to Dendrolembidium. As to taxonomic position, interesting differences of opinion occurred in the early 1960's. Schuster (1963) placed the species in a new genus, Megalembidium Schust. , with Lembidium insulanum as the type; in that paper Schuster also included M. dendroides (earring. & Pears .) Schust. , with the type from Blue Mts, Australia. Grolle (l964a) transferred both Lembidium insulanum and L. dendroides to Kurzia, and in the same year Grolle (l964b) placed Megalembidium as a section of Kurzia subg. Kurzia and Dendrolembidium as a subgenus of Kurzia . Schuster (1980) described and illustrated Megalembidium insulanum; see also Schuster (2000) . Recent collections have revealed additional details of the gametophyte, androecium and gynoecium. Moreover, discovery of mature gynoecia and sporophytes by one of us (lEB) is of considerable significance, and a complete description of the species therefore follows. Plants dendroid, the main erect shoots and branches isophyllous or nearly so, the plants pale green to pure green, the entire upright portion brownish in exposed sites, medium-sized, the leafy axes to 3.5 cm high . Plants with a strongly deve loped system of basal , t Department of Botany, The Field Museum, Chicago, IL 60605-2496, U.S.A. 2 School of Biological Sciences, The University of Auckland, P. B. 92019, Auckland, New Zealand. 82 1. Hattori Bot. Lab. No. 97 2 0 0 5 creeping, plagiotropic rhizomes, from which arise erect, leafy shoots that distally are copiously and 23-pinnately branched; rhizome and leaftess sectors of erect axes giving rise to intercalary, geotropic, microphyllous, rootlike axes, which in turn give rise to intercalary, considerably more slender secondary branches ("secondary roots"). Branches of erect shoot system crowded distally, regular, determinate in length, on one side of axis of Frullania type, on the opposite side of Microlepidozia type, the ultimate branches often weakly cernuous or circinate, the erect shoots unbranched below. Stems of primary aerial axes rigid, comprised of a hyaloderm of numerous, slightly thick-walled, hyaline or pigmented cortical cells that collapse with age, and (1)23 subepidermal layers of small , fuscous, strongly thick-walled cells, grading into a medulla of ± thin-walled colorless cells . Leaves unistratose, those of main aerial axes basal to onset of branches erect, appressed to stem, weakly to distinctly imbricate, ensheathing and hiding much or all of the stem, fragile , hyaline, incubously inserted, deeply concave-cucullate, ovate, the apices narrow, (3)4-dentatelobulate to 0.1; lobes terminating in a single cell or a uniseriate row of 2(3) cells, the lobe cells ± uniform in size and with at most small trigones . Leaves of main aerial axes distal to onset of branches not sheathing the stem, obliquely spreading, more deeply lobed than the leaves below, the lobe cells differentiated: those of uniseriate row and cells immediately below conspicuously larger than those toward lobe base, the latter with bulging trigones. Primary branch leaves smaller, concave, broadly ovate and more broad-based than those of main aerial axis, the apices 3-4-lobulate. Secondary branch leaves smaller than those of primary branches, the apex 23-dentate-lobulate. Tertiary branch leaves smaller than those of secondary branches, the apex short bifid. Cells in median sector of main aerial axes leaves basal to onset of branches somewhat elongated, ± thin walled, with minute trigones; cells in median sector of main aerial axes leaves distal to onset of branches subisodiametric or at most slightly elongated, firm walled, with distinct trigones; surface striate papillose. Oil-bodies totally absent. Underleaves similar to leaves of same shoot-sector except a little smaller and occasionally with one tooth fewer, the underleaves of ultimate branches bidentate-lobulate . Asexual reproduction lacking. Dioecious. Androecia on short, abbreviated, ventraland lateral-intercalary branches from leaftess bases of main aerial axes, the androecia spicate, whitish, variable, sometimes appearing to cease growth and then compact and budlike to vermiform, but at other times proliferating vegetatively with the producuion of several small, sterile, scale-like leaves prior to the formation of a new androecium; bracts strongly ventricose-cucullate, the apex retuse to bidentate; antheridia usually I (at times 2) per bract, the stalk variable, uniseriate throughout or locally with I or a few biseriate tiers. Bracteoles lacking antheridia. Gynoecia on reduced, highly abbreviated ventral-intercalary branches, the gynoecia strongly dorsally assurgent and becoming parallel or nearly so with upright leafy shoots, slender throughout and not swollen and rhizoidous at base; bracts in 4 series that all closely ensheath the gynoecium (including the mature perianth), the bracts concave, appearing membraneous and like onionskin, those of second and third series (from base) often narrowed toward a 23-lobulate apex, the gynoecium also with a few scale-like bractlets at base; bracts and bracteole of innermost series identical or nearly so, firmly attached, erect, mutua lly connivent, together tube-like and tightly ensheathing the lower sector of the perianth, J. J. E NGEL and J. E. BRAGGINS: Austral Hepaticae 37 83 deeply concave-canaliculate, long-elliptic-sublinear, the apices broadly rounded, the apical and subapical cells thin walled and distinctly striate papillose, the apex with 4 rounded projections (lobules) barely perceptible; lamina cells dimorphic, those of a broad median field ± rectangular, with walls strongly thickened and red brown, the surface striolate, those of margin and submargin irregular in shape, with walls thin and pale yellow brown, the surface smooth or faintly striate-papillose, the marginal cells variable in shape, often long and narrow, the apical or free end of marginal cells often divergent and forming a crenulation, the margins otherwise with a few slime papillae. Perianth long emergent, markedly slender and elongate-fusiform (to 9X longer than wide), terete in basal and median sectors, the distal sector obscurely trigonous, pluriplicate, the perianth strongly narrowed, contracted and ± pointed toward the apex; mouth shallowly lobulate, the cells thin walled, rather elongated, laterally free for typically less than 0.5 the cell length but typically free for only very short distances, the mouth thus crenulate-denticulate, the cells at the mouth and those immediately below mouth distinctly striate-papillose; perianth 3(locally 4-) stratose in basal portion. Seta exceptionally long, elevating capsule far beyond level of gametophyte, the seta with 9 rows of very large, firm-walled, outer cells (each with their free face bulging), surrounding an inner core of 2832 much smaller cells. Capsule long linear, with spiral dehiscence, the valves spirally twisted, long linear and strap shaped, the wall 38-46 J1 thick, of 3-4 (locally 5) layers, the outer layer subequal to the combined inner layers, or slightly less thick, the exposed wall firm; outer layer of cells in tiers, rather regularly rectangular, with 2-phase development, the longitudinal walls with well-defined, weakly sinuous, sheetlike thickenings and, sporadically, a few ill-defined nodulelike thickenings alternating with walls that are devoid of thickenings, the transverse walls devoid of thickenings; intermediate layer(s) in cross section thickened in the corners; innermost layer of cells ± tiered, rather regularly, narrowly and markedly long rectangular; semiannular bands common, rather close, usually complete. Spores 11.514.4,u, pale yellow brown, with rather close granular-finely papillose markings and short vermiculae; spore:elater diameter ratio 11.2: 1. Elaters rigid, many nearly perfectly straight, 10.6-12.5 J1 wide, bispiral to tips, the spirals closely wound, notably wide, 4.8-6.2 J1 wide.