| # The grass genera of the world |

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

### Hystrix Moench

From the Greek hustrix (a porcupine), alluding to the inflorescence.

~ Elymus

Including Macrohystrix, Microhystrix

Habit, vegetative morphology. Perennial; caespitose. Culms 60–200 cm high; herbaceous. Culm nodes hairy (puberulent), or glabrous. Culm internodes hollow. Leaves not basally aggregated; auriculate. Sheath margins joined. Leaf blades linear to linear-lanceolate; broad, or narrow; 3–30 mm wide; flat; without cross venation. Ligule an unfringed membrane (tough); truncate; 0.3–1 mm long.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant, or all alike in sexuality; hermaphrodite, or hermaphrodite and sterile (sometimes with sterile spikelets at the tip of the rachis).

Inflorescence. Inflorescence a single spike, or a false spike, with spikelets on contracted axes. Rachides flattened (continuous). Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary to paired; not secund; distichous (in regular rows).

Female-fertile spikelets. Spikelets 8–18 mm long; adaxial; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus present. Callus blunt.

Glumes present (in the lower spikelets, but often missing from the upper spikelets); two (but small), or one per spikelet (the G1 minute or absent); minute, or relatively large; very unequal; shorter than the spikelets; shorter than the adjacent lemmas; free; displaced (to one side); subulate; awned (the outer one awn-like), or awnless; non-carinate. Lower glume 0–1 nerved. Upper glume 1–2 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets.

Female-fertile florets 2–4. Lemmas convex, tapering into long awns; entire; pointed; awned. Awns 1; median; apical; non-geniculate; much longer than the body of the lemma; entered by several veins. Lemmas hairy, or hairless; non-carinate; without a germination flap; 5–7 nerved; with the nerves confluent towards the tip. Palea present; relatively long; 2-nerved; 2-keeled. Lodicules present; free; membranous; ciliate; not toothed; not or scarcely vascularized. Stamens 3. Anthers 2–7 mm long. Ovary apically hairy; without a conspicuous apical appendage. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit adhering to lemma and/or palea; small to medium sized (4–6 mm long); longitudinally grooved; compressed dorsiventrally; with hairs confined to a terminal tuft. Hilum long-linear. Embryo small. Endosperm hard; without lipid; containing only simple starch grains. Embryo without an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals smaller, more regularly rectangular); of similar wall thickness costally and intercostally (thin walled). Mid-intercostal long-cells rectangular to fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata absent or very rare. Intercostal short-cells absent or very rare. Prickles common. Crown cells absent. Costal short-cells neither distinctly grouped into long rows nor predominantly paired (mostly solitary, or adjoining prickle-bases, but occasionally in short rows). Costal silica bodies horizontally-elongated crenate/sinuous.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll without adaxial palisade. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 7. 2n = 28 and 56. 4 and 8 ploid. Haplomic genome content H and S.

Classification. Watson & Dallwitz (1994): Pooideae; Triticodae; Triticeae. Soreng et al. (2015): Pooideae; Triticodae; Triticeae; Hordeinae. 9 species.

Distribution, phytogeography, ecology. Asia, North America, New Zealand.

Mesophytic; shade species and species of open habitats. Woodland and meadows.

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia coronata, Puccinia striiformis, Puccinia montanensis, and Puccinia recondita. Smuts from Ustilaginaceae. Ustilaginaceae — Ustilago.

References, etc. Morphological/taxonomic: Löve 1984. Leaf anatomical: studied by us - H. patula Moench.

Illustrations. • Hystrix duthiei, as Asperella: Hook. Ic pl. 26 (1899). • Hystix patula, as Elymus hystrix: P. Beauv. (1812). • Hystrix gracilis (as Gymnostichum): Hooker, Fl. Novae-Zelandiae (1853).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classifications. See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., Macfarlane, T.D., and Dallwitz, M.J. 1992 onwards. The grass genera of the world: descriptions, illustrations, identification, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classification, pathogens, world and local distribution, and references. Version: 15th June 2025. delta-intkey.com’.

Contents