Genomic constitution

HW, the H genome coming from Hordeum jubatum and its allies, the W genome from Australopyrum. All species are tetraploids with the same genomic constitution. The treatment here differs from that of Connor (1994) in including Elymus enysii. The appropriate combination for E. enysii in Stenostachys has not yet been made.

Distinguishing features

Culms slender; inflorescences drooping to nodding; glumes usually reduced; florets radial to the rachis.

Description

Plants perennial, stoloniferous. Culms 29-80 cm tall, lowest internode 0.6-1.5 mm thick.

Leaves not filiform, 1-4 mm wide, flat, upper surface usually with moderately prominent ribs.

Inflorescence spikelike, nodding or drooping; rachis tough, prolonged for (0.2)0.5-6 mm beyond the base of the most distal spikelet, cross section lunate, lowest internode subequal to or longer than the middle internodes; middle internodes 2-7 mm long; initial disarticulation below the florets, glumes following soon thereafter.

Spikelets solitary, their glumes tangential to the rachis but the florets usually completely or almost radial to the rachis, not pedicellate, lowest spikelet slightly longer than the adjacent internode, middle spikelets from 2-3 times longer than the adjacent internode.

Glumes absent or to 6.7 mm long, shorter than the adjacent lemma, to 0.9 mm wide, subulate to lanceolate but tapering from near midlength to an awnlike tip, membranous with a scarious margin when not subulate, usually scabridulos.

Lemmas usually mostly smooth but scabrous distally, at least over the midvein, sometimes scabrous throughout, usually rounded over the midvein except keeled distally, tips often bidentate, midvein extending into an awn 0.5-6.5 mm. Paleas not winged, tapering in the distal quarter. Lodicules lobed or entire, sometimes ciliate distally. Anthers 1.5-3 mm long.

Some of the information in the above description is taken from Connor and Edgar (2000).

Size

As treated here, Stenostachys includes four species. Connor (1994) and Connor and Edgar (2000) exclude Elymus enysii from the genus because its spikelets are tangential to the rachis and it has better developed glumes than the other three species. The glumes in all four species are tangential to the rachis but deflected back. The basal florets are almost radial to the rachis in E. enysii, but this is less evident than in the other three species because the glumes are wider. For a complete listing, go to http://herbarium.usu.edu/Triticeae/stenost.html

Distribution

Stenostachys is endemic to New Zealand.

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Alternative interpretations

As noted above, the interpretation above differs from that of Connor (1994) and Connor and Edgar (2000) in the inclusion of Elymus enysii.

Type species

Stenostachys narduroides Turcz. [= S. gracilis (Hook. f.) Connor]

Known problems

Australopyrum enysii has not yet been formally transferred to Stenostachys.

Species

Dichotomous key to species

Species pages

References

Connor, H.E. 1994. Indigenous New Zealand Triticeae: Gramineae. New Zealand Journal of Botany 32: 125-154.
Edgar, E.. and H.E. Connor. 2000. Flora of New Zealand, volume 5. Gramineae. Manaaki Whenua Press, Lincoln, New Zealand.

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