Achnatherum caudatum (Trin.) S.W.L.Jacobs & J.Everett
Caespitose, tall, stout, bright green perennial with intravaginal branches with slender purpled inflorescences and cleistogenes in leaf-sheaths at the base. Leaf-sheath 10-20 cm, tough, glabrous, purpled below, margins long hairy above, apical tuft of hairs to 2 mm. Ligule c. 1 mm. Leaf-blade to 50 cm × 3 mm, ± rolled, glabrous, becoming very narrow and finely pointed, abaxially ribbed, glabrous, adaxially with many small prickles on ribs; margins with scattered long (1-1.5 mm) straggling hairs and prickle-teeth. Culm erect, to 1 m, nodes swollen, glabrous, internodes glabrous. Inflorescence to 30 cm, narrow, subtended by tufts of hairs, branches to 10 cm in fascicles similarly subtended, compound; rachis ridged, smooth; branches and pedicels short stiff hairy, naked below. Glumes ± equal, 7-8 mm, including lemma, conspicuously 3-nerved, awn tipped (1.3-1.5 mm), keel short stiff hairy, small prickles in internerves, centrally purple, hyaline elsewhere turning brown, margins ciliate below. Lemma 5-5.5 mm, fusiform, 5-nerved, purple towards margins, fading brown, lobes minute or 0, coma 0.5-1.0 mm, margins contiguous, keel and outer margins long (0.5-0.7 mm) hairy, minutely tuberculate elsewhere; awn to 18 mm, 1-geniculate, column 6-9 mm, arista to 10 mm. Palea 4.5-5 mm, lightly purpled, 2-nerved, internerve hairs reaching almost to ciliate apex. Callus to 1 mm, ± blunt, hairs to 1 mm. Lodicules 3, 1.2-2.0 mm, nerved. Anthers 2.5-3 mm in chasmogamous flowers, penicillate. Gynoecium: ovary 0.75-1.0 mm, trigonous; stigma-styles 1.75-2.0 mm, eccentric. Caryopsis 3 mm, obovate, irregularly ribbed, bases of old style eccentric, keeled opposite linear hilum to 2.5 mm, faintly rugose; embryo 1 mm. Chasmogamous in aerial inflorescences; cleistogamous in reduced inflorescences at culm nodes; cleistogenes in basal leaf-sheaths.
S.: Known only from Canterbury (Amberley) and Christchurch City.
Naturalised from South America.
In aerial inflorescences the caryopsis is so swollen that the lemma and palea are widely opened, and the caryopsis appears to be ready to fall free.
Ensheathed inflorescences at culm nodes bear florets as in aerial inflorescences but anthers are shorter (1.25 mm); caryopses as in aerial florets but appear more coriaceous.
Dark coloured, indurate cleistogenes are present on short inflorescences with glabrous or sparsely hairy branches of up to 8 spikelets on short hairy culms in leaf-sheaths of up to 4 successive culm nodes and up to 3 successive nodes of vegetative shoots. Spikelets are subtended by tufts of hairs to 1 mm; glumes c. 7 mm, 3-nerved, papery, becoming acute; lemma to 5 mm, apiculate, 1-nerved, brown, keel long hairy; palea 3-3.5 mm, 2-nerved, internerve hairy; anthers 3, 0.5-1.0 mm, barbed not penicillate, persisting on stigma-styles of caryopses; caryopsis 4-4.5 mm × 4-5 mm wide > aerial caryopsis, styles eccentric, pericarp dark, extremely coriaceous.
This taxon is distinguished by the criteria in Torres, M. A. Monographia 12 Prov. Buenos Aires Comisión Invest. Cien. (1993) and Monographia 13 (1997) where it is treated as a species of Stipa L.
