Volume V (2000) - Flora of New Zealand Gramineae
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Trisetum Pers.

Trisetum Pers., 1805

Type species: T. pratense Pers.  nom. illeg.

Perennials, tufted or rhizomatous; branching extravaginal or rarely intravaginal. Ligule membranous, truncate or rounded, often ciliolate. Leaf-blades linear, narrow, flat or involute. Inflorescence a contracted to lax panicle. Spikelets 2-several-flowered, laterally compressed; disarticulation above glumes and between lemmas; rachilla usually hairy, prolonged. Glumes unequal to subequal, < to ≈ spikelets, keeled, not awned; lower 1-3-nerved, upper 3-5-nerved. Lemma membranous to thinly coriaceous, 3-7-nerved, keeled, bidentate or bicuspid, dorsally awned from upper ½; awn reflexed, or geniculate (not N.Z. spp.). Palea gaping, silvery, thinner than lemma, 2-keeled. Callus short, hairy. Flowers ⚥, chasmogamous or cleistogamous. Lodicules 2, membranous, glabrous or ciliate. Stamens 3. Ovary glabrous; styles free. Caryopsis slightly compressed laterally; embryo small; hilum short; endosperm liquid. Fig. 10.

Key

1
Glumes markedly dissimilar in shape, the lower linear-lanceolate or narrow-oblong, the upper elliptic-lanceolate to ovate, unequal in length, the lower < upper
2
Glumes ± similar in shape, the lower narrow-elliptic, the upper elliptic-ovate, ± equal in length
8
2
Panicle very lax, with individual spikelets mostly conspicuous
Panicle compact or interrupted at base, or somewhat open but with spikelets clustered and not individually conspicuous
3
3
Culms with long straight soft hairs above nodes and few elsewhere, or densely pilose or pubescent throughout
4
Culms glabrous throughout, or sometimes minutely pubescent above basal nodes or below panicle
6
4
Panicle compact or interrupted at base, rachis hidden except near base
Panicle somewhat open, rachis clearly visible
5
5
Lemma 5-7.5 mm; awn ≥ lemma; leaf-blade flat or rarely inrolled, 1.3-3 mm wide
Lemma 3-4.5 mm; awn ≤ lemma; leaf-blade inrolled, < 1 mm diam., rarely flat and up to 2 mm wide
6
Tufts open; panicle whitish or pale straw-coloured, sometimes purple-tinged
Tufts dense; panicle grey- or light-green to brownish red or amber
7
7
Panicle compact, dense, oblong, sometimes with spreading lower branches; leaf-blade abaxially glabrous, scabrid above
Panicle ± interrupted, not very dense, lanceolate, shortly branched throughout; leaf-blade abaxially densely minutely scabrid or sometimes smooth throughout or sparsely scabrid above
8
Panicle compact, or interrupted at base, rachis hidden except near base; culms often villous to shortly sparsely pubescent, usually not much overtopping leaves
Panicle ± spike-like but rachis visible, lower branches sometimes slightly distant; culms glabrous, occasionally villous or pubescent, usually far overtopping leaves
9
9
Spikelets 5.5-8 mm; panicle 3-15-(24) cm; leaf-blade 1-7 mm wide
Spikelets (3.5)-4-5.5 mm; panicle 0.5-8.5 cm; leaf-blade 0.3-1.5-(2) mm wide

c. 85 spp., of temperate regions throughout the world. Meadows, mountain slopes, upland grasslands, weedy places. Endemic spp. 7, indigenous spp. 2.

N.Z. spp. of Trisetum were revised by Edgar, E. N.Z. J. Bot. 36: 539-564 (1998), incorporating the intensive field observations of A. P. Druce. Most species are variable, especially in form of leaf-blade and in culm vesture. In general Trisetum is found in N.Z. on rocky sites: on limestone or marble cliffs, or on bluffs; in alpine herbfield, fellfield or scree; and on ultramafic sites. Three species, T. lasiorhachis, T. lepidum and T. youngii occur in scrub, open forest or tussock grassland.

All species are very variable. Features normally characteristic of a species are not invariably present and it was not feasible to include every variant in the key.

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