Deyeuxia youngii (Hook.f.) Buchanan
≡Agrostis youngii Hook.f. Handbk N.Z. Fl. 330 (1864)
≡Calamagrostis youngii (Hook.f.) Petrie, T.N.Z.I. 47: 57 (1915)
≡Deyeuxia youngii (Hook.f.) Buchanan var. youngii (autonym Hackel in Cheeseman 1925 op. cit. p. 162);
Holotype: K! J. Haast Canterbury, New Zealand, 1862.
=Calamagrostis petriei Hack., T.N.Z.I. 35: 380 (1903)
≡Deyeuxia petriei (Hack.) Cheeseman Man. N.Z. Fl. 872 (1906)
≡Calamagrostis youngii var. petriei (Hack.) Petrie, T.N.Z.I. 47: 57 (1915)
≡Deyeuxia youngii var. petriei (Hack.) Cheeseman Man. N.Z. Fl. 162 (1925);
Holotype: W 29192! D. Petrie Swampy Hill, 1500 ft, Dunedin (No 1190 to Hackel).
Tufts rather narrow, 30-130 cm; branching extravaginal. Leaf-sheath chartaceous with membranous margins, distinctly ribbed, glabrous or finely hairy, light green to light brown. Ligule 0.8-2.5 mm, truncate, ciliate to lacerate, abaxially smooth, or densely minutely pubescent-scabrid. Leaf-blade 12-35-(60) cm × 1-4 mm, stiff, flat to frequently rolled, especially towards tip, abaxially smooth, adaxially distinctly ribbed and finely scabrid on ribs; margins finely scabrid, tip filiform, acute. Culm 40-115 cm, nodes conspicuous, internodes mostly smooth, but sparsely scabrid below panicle. Panicle 7-16-(22) cm × 5-23 mm, linear-lanceolate, shortly and narrowly branched, or more open below; rachis smooth, branches slightly scabrid, with ± densely crowded spikelets on slightly scabrid pedicels. Spikelets 4.5-7.5 mm, light green or purplish. Glumes 1-nerved, submembranous, elliptic-lanceolate, acute, scabrid near apex, keel scabrid. Lemma (4)-5-6 mm, ≈ glumes, subcoriaceous, scabrid, elliptic-lanceolate, apex denticulate; awn (0.5)-1-3 mm, straight, from upper ⅓ of lemma or rarely middorsal, usually barely reaching but occasionally overtopping lemma apex, rarely awn 0. Palea ˜ lemma, keels and interkeel scabrid. Callus hairs fine, ± dense, c. ½ length of lemma. Rachilla prolongation 1.5-2.5 mm, tipped by dense tuft of fine hairs 2-3-(3.5) mm, almost reaching lemma apex. Lodicules 0.6-0.8 mm, linear, acute. Anthers 1.2-1.9 mm, penicillate. Caryopsis 2.5-3 × 0.7-1 mm.
S.: north-west Nelson at Lake Sylvester, Marlborough on Chalk Range and on Mt Fyffe, scattered localities in Mid and South Canterbury and Otago. Tussock grassland, shrubland and open sites, and on rocky sites; lowland to alpine.
Endemic.
REPRODUCTIVE BIOLOGY
Cleistogamous flowers occur throughout the range of D. avenoides. Plants with cleistogamous flowers usually have more slender culms, much shorter anthers and narrower panicles than plants with chasmogamous flowers. There is no geographical separation and plants with cleistogamous flowers may be found growing close to plants with chasmogamous flowers.
A plant of D. quadriseta growing in the wild at Taita had cleistogamous flowers and anthers 0.4 mm (CHR 179594 A. P. Druce 1967) and another from nearby had chasmogamous flowers and anthers 0.6-0.7 mm (CHR 179595 A. P. Druce 1967).
All known specimens of D. lacustris are cleistogamous.
Deyeuxia youngii has only been collected from scattered localities.
Deyeuxia youngii is the only sp. of Deyeuxia with penicillate anthers. In tribe Agrostideae this type of anther is otherwise found only in Dichelachne Endl. which has spp. with penicillate and spp. with non-penicillate anthers.
