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Tuatara: Volume 28, Issue 2, February 1986

Notes on Some Anthocerotae of New Zealand (5)

page 83

Notes on Some Anthocerotae of New Zealand (5)

Key words: Anthocerotae, Dendroceros allisonii, Dendroceros endiviaefolius, Dendroceros giganteus, Dendroccros granulatus, Dendroceros megasporus, Dendroceros nodulosus, Dendroceros validus.

Abstract

The taxonomy, morphology and distribution of Dendroceros giganteus (Lehm. & Lindenb.) Prosk., D. granulatus Mitt, and D. validus Steph. are reported. D. allisonii Herz., D. endiviaefolius (Mont.) Prosk., D. megasporus Herz. and D. nodulosus Steph. are reduced to synonymy.

The Genus Dendroceros

Key to New Zealand species.
1 Plant large, up to 5cm long, terrestrial, growing over other bryophytes or litterD. giganteus
Plants small, 1 (−3) cm long, epiphytic on bark or twigs2
2 Epidermis of capsule trabeculateD. validus
Epidermis of capsule noduloseD. granulatus

(i) Dendroceros giganteus (Lehm. and Lindenb.) Prosk.

(Synonymous with Dendroceros endiviaefolius (Mont.) Prosk. and Anthoceros colensoi Mitt.)

(a) Distribution

In New Zealand this very beautiful species is found growing as a caespitose carpet overlying mosses, liverworts or water-retentive litter in swampy ground in regions of high rainfall, as in Fiordland, Arthur's Pass and the Ruahine Range. It occurs also on the Auckland Islands (collected P. N. Johnson — Welt H 4495) and in Chile and Argentina where it has been known as D. endiviaefolius — a name regarded here as a synonym.

(b) References and sources of material.

At the British Museum I was able to examine the type material by courtesy of the Curator of Bryophytes. Other specimens that I examined came from the herbaria of the British Museum, the New York Botanical Garden, National Museum at Wellington, Botany Division at Christchurch and E. A. Hodgson at Massey University. Living plants were collected at Arthur's Pass, Milford Sound, Wilmot Pass and Mt. Cargill and grown in culture at Massey University. The species was first named Anthoceros giganteus (Lehmann, 1832), then transferred to Megaccros (Stephani, 1916) and later to Dendroceros (Proskauer, 1953). Proskauer remarked on its similarity to D. endiviaefolius of Chile and Argentina, as had Schiffner earlier (1890) using the name Anthoceros. Detailed notes and illustrations of D. endiviaefolius are given by Proskauer (1953) and by Hassel de Menendez (1962). Mitten (1855) described Anthoceros colensoi from specimens collected on the summit of the Ruahine mountains and now housed at the New York Botanical Garden. Already Proskauer (1953) has used the name Dendroceros giganteus for these plants. Goebel used living New Zealand plants in his studies (1905, 1906) but Khanna (1944) unfortunately, as Proskauer (1953) noted, did not have correct material of this species.

(c) Morphology of the gametophyte.

The bright-green, strap-shaped thallus, up to 5 cm long and 1.5-5(−8)mm wide, may branch a few times (Fig. 1). It consists of a flat or slightly convex midrib region and wide unistratose wings, which are deeply cut into rounded fimbriate lobes, that at times are so greatly folded that they completely obscure the midrib. However, in young parts of the thallus the wings are absent. The tip itself is slightly coiled (Fig. 3). Rhizoids are page 84
Fig. 1 Plant of Dendroceros giganteus. Photo by L. Maiden.

Fig. 1 Plant of Dendroceros giganteus. Photo by L. Maiden.

Fig. 2 Plant with sporophytes. Photo by L. Maiden.

Fig. 2 Plant with sporophytes. Photo by L. Maiden.

infrequent, with the result that the plant is only loosely attached to the underlying vegetation. In older plants adventitious branches arise ventrally from one or other side of the midrib, and may become detached from the main plant. Plants are monoecious. Antheridia occur singly in antheridial cavities which are widely dispersed or in groups of 3 to 4 on the midrib. Archegonia too occur on the midrib and later usually a single sporophyte develops on each branch (Fig. 2).

(d) Anatomy of the thallus

The midrib region is up to 27 cells high. Above and below are small cells each with 1-4 disc-shaped chloroplasts. The central cells are larger with up to 8 chloroplasts except for scattered cells containing mucilage. They are somewhat elongated in an axial direction and often their walls appear pitted due to enlarged primary pit fields. Pores are present on the underside of the thallus leading into cavities. These may become page 85
Fig. 3 Young thallus. Photo by L. Maiden.

Fig. 3 Young thallus. Photo by L. Maiden.

occupied by Nostoc colonies which usually grow so large that they protrude from the surface.

The wings develop late from a marginal meristem, resulting in a regular cell arrangement similar to that derived from a cambium. They are unistratose and except in the scattered mucilage cells have 1-4 disc-shaped chloroplasts per cell.

(e) Morphology of the sporophyte

The slender brown capsule lacks stomata and is up to 8cm long and 0.3mm wide (Fig. 2). It is surrounded at the base by an involucre, 2cm high, which gradually tapers upwards from a basal width of 2mm. When ripe the capsule splits some distance below the apex into 2 valves which remain united at the tip and twist spirally. The spores when shed are green, unicellular and up to 58 m in diameter. The inner face is finely dotted (punctate) and has an indistinct triradiate marking (Fig. 4a.); the spherical face is punctate and verrucose, with irregular knob-like protuberances 2.5um high (Fig. 4b). The elaters are 180-250um long and have a maximum width of 8-12 m narrowing somewhat towards the tips; they are made of 2-4 cells with a pale-brown helical band.

(ii) Dendroceros validus Steph.

(Synonymous with Dendroceros allisonii Herz.)

(a) Distribution

This species was collected by Schiffner in 1894 on Mt Singalang. Bonner (1965) gives the distribution as Sumatra and Philippines. Plants from New Zealand, which are now considered to belong to this species, were first collected by K. W. Allison on 2/9/1932 from a tree trunk near the edge of bush, south of Rotorua. Later it was found by W. Martin on logs in forest at Pegasus, Stewart Island on 9/1/1949, by S. Courtney, F. Overmars and H. Wilson on a twig of Lophomyrtus bullata near a stream in Pelorus Bridge Scenic Reserve, Marlborough on 30/9/1983 and independently by B. V.

Sneddon on 9/12/1984 and by T. Moss on 10/12/1984 in the Akatarawa Range. page 86
Fig 4 Spore of D. giganteus (a) triradiate face (b) spherical face. Scanning electron micrographs by G. Walker.

Fig 4 Spore of D. giganteus (a) triradiate face (b) spherical face. Scanning electron micrographs by G. Walker.

Probably it has been overlooked in other New Zealand localities for it grows intermixed with other epiphytes and is obvious only when sporophytes are present. (Fig. 5).

(b) References and sources of material

Dendroceros validus was first described by Stephani (1917) from Schiffner's specimen which is now housed in the Herbarium at Geneva. A more complete description in English, accompanied by several illustrations, was provided by Hasegawa (1980). Herzog (1935) gave a Latin description of what he named D. allisonii, using a New Zealand specimen which had been collected by K. W. Allison and forwarded by E. A. Hodgson. The holotype, Hodgson 142, is now housed at Jena. Isotypes are in the herbaria of Botany Division and of E. A. Hodgson. The latter (MPN 20700) and also the specimen collected by W. Martin (MPN 20701) were available for examination. Plants found at Pelorus Bridge Scenic Reserve were able to be photographed and examined in living condition and were kept in culture for several months.

(c) Morphology of the gametophyte

The thallus is green in colour and about 1cm long and 5mm broad. It may branch a few times. There is an ill-defined midrib region, about 0.3mm wide, which is flat above and convex below and thin, broad, crispate wings which often become so strongly folded and curved upwards that they obscure the midrib (Fig. 6). Short rhizoids arising ventrally from the midrib attach the plant to twigs or bark. Plants are monoecious. Antheridia occur singly in antheridial cavities on the midrib, in which position archegonia and later sporophytes are also located.

(d) Anatomy of the thallus

The midrib region, as seen in transverse section, is compact (Figs 7 & 8). Medianly it is 6 cells (0.12mm) deep, but becomes thinner as it merges into the wings which are only one cell deep. The internal cells show conspicuous simple pits on the walls and usually contain a single chloroplast. Those of the upper surface each have a somewhat thickened outer wall and one large chloroplast while some of those on the lower surface produce rhizoids. On both surfaces near the apex, pores are present and further back Nostoc colonies bulge strongly from the lower side of the thallus. In the wings each cell, except for occasional mucilage cells, has a single large chloroplast of irregular shape.

page 87

Often at the angles where the cells meet there are small corner thickenings (trigones) or sometimes these are perforated so leaving air-filled regions (Fig. 9). The outer walls of the cells are somewhat thickened.

(e) Morphology of the sporophyte

The sporophyte, 8-15mm high, is at first green and is surrounded at the base by a brown cylindrical involucre 3-5mm high. The capsule lacks stomata and on the outside has a trabeculate appearance due to the outermost cells having thickened lateral walls (Fig. 10). When ripe it splits from the apex downwards into 2 valves which turn chestnut-brown and undergo slight twisting. The spores, 60-65 um in diameter, are multicellular when shed. Their surface is finely punctate (Figs. 11a & 11b) and has a weak triradiate marking (Fig. 11a). The elaters consisting usually of 3 cells, are 200 um long and show a helical band of thickening.

(iii) Dendroceros granulatus Mitt.

(Synonymous with Dendroceros nodulosus Steph. and Dendroceros megasporus Herz.)

(a) Distribution

Dendroceros granulatus is widely distributed in the islands of tropical Asia and the South Pacific (Hasegawa, 1984). Plants considered to belong to this species are found in northern New Zealand as far south as Wairoa. They grow as an epiphyte intermixed with other bryophytes on the trunks of nikau palm, Rhopalostylis sapida Wendl. & Drude, and on the stems of trees and shrubs such as manuka, Leptospermum scoparium J. R. and G. Forst. and kanuka, L. ericoidies A. Rich. (Kunzea ericoides (A. Rich) J. Thompson).

(b) References and sources of material

Dendroceros granulatus was first described by Mitten (1871) from plants collected in Samoa by Powell. Later Stephani (1917) described it separately and also listed it as a synonym of D. javanicus Nees. Unfortunately Stephani's outline drawing (sheet 2248) shows little detail. A more complete description accompanied by illustrations is given by Hasegawa (1982), who kindly supplied a duplicate specimen collected in 1982 in New Caledonia (N. Kitagawa 22259). The name D. nodulosus was given by Stephani (1909; 1917) when he described a specimen collected by Cheeseman in Auckland in 1895 and now housed in the Stephani Herbarium, Geneva. Notes and drawings made by Stephani (sheet 2299) were available for study by courtesy of the curator of the Stephani Herbarium. The species has been collected frequently in New Zealand and is represented in the herbaria of E. A. Hodgson, National Museum and Botany Division. A specimen collected last century by Andrew Sinclair, which is on the sheet of Anthoceros colensoi in the Mitten Herbarium, has been annotated by Proskauer as presumably D. nodulosus. D. megasporus was established by Herzog (1935) who provided a Latin description based on a specimen which had been forwarded by E. A. Hodgson and had been collected by L. B. Moore 17/5/1933 on manuka at Te Moehau, Auckland. The holotype, Hodgson 141, is now housed at Jena. Isotypes are in the herbaria of Botany Division, Christchurch and of E. A. Hodgson. The latter, MPN 20706, has been determined as D. nodulosus by W. E. Nicholson. I can find no significant differences between the specimens and consider that all belong to D. granulatus. The description given below is based on fresh material collected from Piha, Auckland, New Zealand and maintained in culture at Massey University.

(c) Morphology of the gametophyte

The thallus is green in colour and up to 3cm long and 2.5mm wide. It may branch a few times (Figs. 91 & 13). There is a midrib region, up to 0.8mm wide, which is flat above and convex below, and broad wings which are deeply lobed and under moist conditions a little crispate. However, on drying the wings curl upwards strongly. A few short rhizoids may be present on the under side of the midrib. Plants are monoecious. page 88
Fig. 5 Plants of Dendroceros validus on twig of Lophomyrtus. Photo by L. Maiden.

Fig. 5 Plants of Dendroceros validus on twig of Lophomyrtus. Photo by L. Maiden.

Fig. 6 Part of the thallus. Drawing by C. A. Korndorffer.

Fig. 6 Part of the thallus. Drawing by C. A. Korndorffer.

page 89
Fig. 7 Transverse section of the midrib.

Fig. 7 Transverse section of the midrib.

Fig. 8 Cell detail of part of 7.

Fig. 8 Cell detail of part of 7.

Fig. 9 Part of the wing.

Fig. 9 Part of the wing.

Fig. 10 Epidermis of the capsule.

Fig. 10 Epidermis of the capsule.

page 90
Fig. 11 Spore of D. validus (a) triradiate face (b) spherical face. Scanning electron micrographs by G. Walker.

Fig. 11 Spore of D. validus (a) triradiate face (b) spherical face. Scanning electron micrographs by G. Walker.

Antheridial cavities, each containing one large antheridium, are aggregated on the midrib, while a few archegonia, later followed by sporophytes, also appear in this position either on the same or on adjacent branches.

(d) Anatomy of the thallus

As seen in a transverse section the midrib region is compact (Figs. 14 & 15). Medianly it is up to 11 cells (0.26mm) deep but towards the wings it gradually becomes thinner. The upper and lower cells have a single chloroplast of irregular shape while the latter may show a somewhat thickened exterior wall. Large blue-green algal colonies, forming within pores, produce prominent projections on the lower surface and occasionally on the upper surface also. The central cells each have 1 or 2 chloroplasts and often show trigone thickenings at the angles and a reticulate appearance on the lateral walls due to large primary pit fields. (Fig. 15). The wings are unistratose and, except in the scattered mucilage cells, have one large chloroplast per cell. At times there are triangular or rectangular trigones at the angles and these may be perforated (Fig. 16). As well, in older parts of the thallus, there are a few larger perforations where one or more mucilage cells have broken down (Fig. 17).

(e) Morphology of the sporophyte

The sporophyte, usually only 10mm high, is surrounded at the base by a tuberculate involucre 4-5mm high. The capsule lacks stomata and is at first green but later turns chestnut brown. It is described as nodulose because of prominent thickenings on the lateral walls of the epidermal cells (Fig. 18). When ripe it opens at the top by a slit on one side, then flattens and twists slightly as the slit lengthens. The spores are green and multicellular when shed, with a diameter of 55-80 m. The surface (Figs 19a & b) is punctate (dotted) except at the weak triradiate marking (Fig. 19a). Elaters consisting of 3-5 cells are up to 400 m long and have a pale brown, helical band.

Note: Once the spores are shed regeneration takes place by new shoots developing at the margin of the thallus and the old plant tends to die off.

Acknowledgements

The writer is deeply indebted to J. Hasegawa for information and helpful discussion regarding Dendroceros species found in the islands of the South Pacific and of tropical Asia; to the curators of the herbaria at Botany Division, National Museum, British page 91
Fig. 12 A group of plants of Dendroceros granulatus. Photo by L. Maiden.

Fig. 12 A group of plants of Dendroceros granulatus. Photo by L. Maiden.

Fig. 13 A single plant. Photo by L. Maiden.

Fig. 13 A single plant. Photo by L. Maiden.

page 92
Fig. 14 Transverse section of the midrib.

Fig. 14 Transverse section of the midrib.

Fig. 15 Cell detail of part of 14.

Fig. 15 Cell detail of part of 14.

Fig. 16 Part of the wing (young thallus).

Fig. 16 Part of the wing (young thallus).

Fig. 17 Part of the wing (older thallus) Note large perforations as well as small ones.

Fig. 17 Part of the wing (older thallus) Note large perforations as well as small ones.

Fig. 18 Epidermis of the capsule.

Fig. 18 Epidermis of the capsule.

page 93
Fig. 19 Spore of D. granulatus (a) triradiate face (b) spherical face. Scanning electron micrographs by G. Walker.

Fig. 19 Spore of D. granulatus (a) triradiate face (b) spherical face. Scanning electron micrographs by G. Walker.

Museum, New York Botanical Garden, Geneva and Jena for information and the loan of specimens; also J. Beever, J. Braggins, J. Child, C. Meurk, A. Ratkowsky and H. Wilson for assistance with the collection of material.