Simonachne maidenii ( A . A .Ham.) E . J .Thomps. 2022

Thompson, E. J., 2022, Simonachne, a new genus for Australia segregated from Ancistrachne s. l. (Poaceae: Panicoideae: Paniceae) and a new subtribe Cleistochloinae, Australian Systematic Botany 35 (1), pp. 19-62 : 41-42

Simonachne maidenii ( A. A.Ham.) E. J.Thomps. , comb. nov.

Eriochloa maidenii A. A. Ham., Proc. Linn. Soc . N. S. W. 37: 709 (1912); Ancistrachne maidenii ( A. A. Ham.) Vickery, Contrib . N. S. W. Natl. Herb. 3(2): 83 (1961). Type: New South Wales. Hawkesbury River , 3 May 1912, A. A. Hamilton s.n. (holo: NSW [ NSW52514 , JSTOR photo!]; iso: BRI [ AQ540088 ,!], NSW [ NSW520052 , JSTOR photo!]) .

Fertile branches ascending to 40 cm high, copiously branched with up to ~12 nodes. Fertile culm internodes up to 4.5 cm long. Mature fertile leaf sheaths retained, convolute, pilose; outer margin ciliate with ascending tuberculate-based simple trichomes upto 0.5 mm long. Leaf blades upto 4.5 cm long and 7 mm wide; lower margin with tuberculate-based simple trichomes upto 3 mm long. Ligule 0.3 mm long. Contraligule 0.1 mm long. Mid-culm leaf blades 2.5–4.5 cm long, 2.5–4.0 mm wide, apex tapering, base truncate, margins white; both surfaces sparsely pubescent with simple trichomes upto 0.8 mm long. Terminal inflorescences on axes 1.5–5.5 cm long, 8–32-flowered; 0–several branches, appressed, rachis upto 1 cm long, 1–6-flowered. Spikelets 2.6–2.9 mm long, 1.0– 1.1 mm wide; lateral pedicels 0.4–1.0 mm long, ultimate pedicel 0.5–2.0 mm long. Lower glume lunar, ~ 0.2 mm long, apex obtuse. Upper glume ovate, 2.6–2.9 mm long, apex acute, margins inrolled. Lower lemma ovate, 2.6–3.0 mm long; apex acute, margins inrolled. Upper lemma 2.4–2.6 mm long; apical cilia 60–90 µm long, mucronate to shortly awned. Lodicules ∼ 0.2 mm long. Upper palea 2.4–2.6 mm long; apex acute. Anthers 1.5 mm long. Caryopsis ~ 1.7 mm long, ~ 0.8 mm wide, rarely present. Axillary inflorescences usually present below apical 2 or 3 internodes; 3- or 4-flowered, lowest 1 or 2 enclosed in leaf sheath. Spikelets 2.8–3.2 mm long, 1.2–1.3 mm wide. Lower glume vestigial upto 0.1 mm long. Upper glume ovate, 2.8–3.2 mm long, chartaceous, villous with woolly hairs upto 0.2 mm long; apex obtuse. Lower lemma ovate, 2.7–3.2 mm long; apex revolute. Upper lemma 2.2–2.4 mm long; apex revolute, cilia 60–90 µm long, mucronate to shortly awned. Upper palea 2.2–2.4 mm long; apex revolute. Anthers 0.2 mm long. Caryopsis 1.4–1.9 mm long, 0.7–0.9 mm wide; surface minutely longitudinally striate; light brown. Fig. 1 , 2 , Appendix 19.

Illustrations

D. J. B. Wheeler, S. W. L. Jacobs and B. E. Norton, Grasses of New South Wales 93 (1982); S. W. L. Jacobs and C. A. Wall in G. J. Harden (ed.), Flora of New South Wales 4: 452-3 (1993).

Additional specimens examined

NEW SOUTH WALES. Along an ephemeral creekline close to Old Great North Road, Devines Hill , 29 January 1999, P. Pike s.n. ( NSW 427980 ); Singleton Road, Wiseman Ferry , 23 January 1999, P. Pike s.n. ( NSW 427981 ); Erskine Creek downstream from Jack Evans track in the Blue Mountains National Park , 6 March 1999, R. G. Coveny 17686 & Hind ( BRI AQ681893 ); 20 m E of Glenreagh – Grafton road, 7 km N of Glenreagh, 6 July 2001, G. Elks s.n. ( NSW 488035 ); ~ 5 km along Stockyard Creek Road from Punchbowl Road , ~ 25 km NW by N of Grafton, 28 November 2005, Edwards 3 ( NSW 618071 ); on left-hand side of track along Marramarra Creek ~ 20 m from Smugglers Ridge and Marramarra Ridge track exits, 17 November 2006, P. Pike s.n. ( NSW 772920 ); Sandstone Drive, S of Bull paddock, Orara River , 3 January 2011, G. Clancy s.n. ( NSW 882378 ); Porto Ridge , SW of Brooklyn, May 2011, R. G. Coveny 19454 ( NSW 891751 ); Stockyard Creek, along Stockyard Creek Rd , ~ 30 km NNW of Grafton, 5 June 2013, E. J. Thompson EJT936 ( BRI AQ1012262 ); near Whiporie, along Summerland Way , ~ 55 km N of Grafton , 5 June 2013, E. J. Thompson EJT939 ( BRI AQ1012263 ); Coaldale, edge of Coaldale Rd nr. junction with Stockyard Creek Rd , ~ 31 km NNW of Grafton, 22 June 2013, E. J. Thompson EJT945 & G. P . Guymer ( BRI AQ1012265 ); along Benowie walking track adjacent to Sams Creek, Berowa , September 2015, E. J. Thompson EJT1038 & G. P . Guymer ( BRI AQ 971047 ). CULTIVATED. Ashgrove (ex Stockyard Creek Road ), April 2017, E. J. Thompson MOR815 ( BRI AQ1022226 ) .

Distribution

Occurs in two disjunct populations on the New South Wales coastline ( Fig. 3 ).

Habitat and ecology

Under a canopy of trees or shrubs on sandy soils derived from sandstone.

Phenology

Dates of herbarium collections indicate that S. maidenii flowers throughout the year. Cultivated plants flower mostly in summer.

Conservation status

Listed as Vulnerable under the Biodiversity Conservation Act 2016, New South Wales.

Notes

Simonachne maidenii shares morphological characters with all of the other taxa in subtribe Cleistochloinae ( Table 1 ). Notable similarities include S. maidenii and Calyptochloa spp. having a contraligule and the stoloniferous growth habit, giving plants a very similar appearance in the field.

Breeding system

The type of CL manifested by Simonachne maidenii fits the category of dimorphic anthers with amphigamy in the classification of CL by Thompson (2017). Axillary CL in S. maidenii is obligate, whereas in Ancistrachne, CL is facultative with the CL and CH anthers, the same size fitting the type ‘monomorphic CH and CL anthers’ on the same plant as defined by Thompson (2017).

Micromorphology and macromorphology of the lemmas and palea

Simonachne maidenii and Ancistrachne s.s. differ in the lower lemmas by S. maidenii having absence of prickles and film of epicuticular wax. Upper lemmas of S. maidenii have minute longitudinal ridges and lack papillae. Upper lemmas of the terminal spikelets of S. maidenii are chartaceous to slightly hardened and loosely clasping the caryopsis, whereas for Ancistrachne s.s. they are hardened, glossy and tightly clasping the caryopsis. Simonachne maidenii , as for other species in Cleistochloinae , lacks a lower palea, whereas species of Ancistrachne , members of Neurachninae s.s. and the species of Panicum have a lower palea. Simonachne maidenii differs from Ancistrachne by the indumentum on the upper glume and lower lemma and differs from other members of Cleistochloinae by having an indistinct germination flap on the upper lemma ( Tables 1 , 3 , Fig. 4 ; Appendices 8, 10–13).

Abaxial leaf-blade epidermis

Costal−intercostal zonation conspicuous. Papillae absent. Costal long cells rectangular, much narrower than intercostal; anticlinal walls of intercostal long cells Ω-shaped. Anticlinal walls of intercostal long cells moderately undulating, often irregular with short-wave length. Stomata 38–43 µm long with low triangular subsidiaries, in 2 rows separated by 5–6 files of long cells. Bicellular microhairs 52–56 µm long, proximal cell longer than distal, occasional. Silica bodies in single rows, bilobate and polylobate, 16–25 µm long, common. Hooks present (Appendices 14, 15).

The shape of the anticlinal walls of long cells in the upper lemmas and the abaxial leaf surface in A. maidenii differ from those in A. uncinulata , and, in A. maidenii , the shapes of these walls differ from each other ( Table 3 ). Such differences in the shape of anticlinal walls of long cells have been reported for some other panicoid grasses ( Lu et al. 2009; Harun et al. 2020).

Transverse section of leaf blade

C 3; XyMS+. Mesophyll with radiate chlorenchyma; adaxial pallisade chlorenchyma present. Midrib not prominent; with a double bundle sheath; outer complete ring of parenchyma cells and partial inner ring of thick-walled cells with adaxial arc of clear parenchyma cells. Bulliform cells in discrete regular groups; in simple fans. Sclerenchyma accompanying all vascular bundles as adaxial strands and abaxial girders (Appendix 16).

Transverse section of culm

Culm examined 0.6 mm in diameter. Outer smallest vascular bundles adjacent to tangential girder sclerenchyma and imbedded in large-celled sclerenchyma. Vascular bundles with a ring of clear parenchyma; three sizes in separate circles, smallest to the periphery. Chlorenchyma in rectangular blocks, 2 or 3 cells deep by up to 10 cells wide; cells with regular size and shape, more or less circular. Inner ground tissue consisting of large thin-walled cells. (Appendix 17).

The distribution of the bundle sheath parenchyma of S. maidenii has similarities to the fresh culm sections of Entolasia spp. prepared for this study.

Surface of inflorescence culm

Pilose with tuberculate-based macrohairs up to 2 mm long, muriculate with hooks and scabridulous with prickles. Stomata frequent, similar to those on the abaxial leaf surface. Bicellar microhairs, ~44 μm long, occasional. Silica bodies absent. (Appendix 18).

Figures

Fig. 1. Inflorescences of Simonachne maidenii (=Ancistrachne maidenii). (a) Fertile culm of showing amphigamous inflorescences comprising terminal reduced spike-like panicles (TI) and axillary racemes (AI). (b) Terminal inflorescence. (c) Axillary inflorescence. All from Thompson EJT936 (BRI). Photos: Queensland Herbarium. Scale bar: 10 cm.

Fig. 2. (Caption on next page)

Fig. 3. Distribution of Simonachne maidenii (=Ancistrachne maidenii) on the basis of herbarium specimen point data.

Fig. 4. Lower lemmas from chasmogamous spikelets from terminal inflorescences: (a) Simonachne maidenii; (b) Ancistrachne uncinulata; (a) from Thompson EJT936 (BRI) and (b) from Thompson EJT1018 (BRI). Photos: E. J. Thompson. LG1, lower glume; st, stigma emergent at half way along spikelet; wh, woolly hairs; uh, uncinate macrohairs. Scale bar: 2 mm.