The grass genera of the world
From the Greek esperis (western) and Stipa (q.v.).
Including Sparteum P. Beauv.
Sometimes referred to Stipa
Habit, vegetative morphology. Perennial; densely caespitose. Culms 30–100 cm high; herbaceous; branched above, or unbranched above (?). Culm nodes hairy, or glabrous (?). Culm internodes solid, or hollow (?). Young shoots intravaginal. Leaves mostly basal, or not basally aggregated (?); auriculate, or non-auriculate (?). Leaf blades linear; narrow; 1–5 mm wide; setaceous, or not setaceous; flat, or folded, or rolled (involute or convolute); without cross venation; persistent; rolled in bud, or once-folded in bud. Ligule an unfringed membrane, or a fringed membrane (?). Contra-ligule present, or absent (?).
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets; inbreeding; exposed-cleistogamous, or chasmogamous, or exposed-cleistogamous and chasmogamous; with hidden cleistogenes, or without hidden cleistogenes (?). The hidden cleistogenes (if present) in the leaf sheaths (?).
Inflorescence. Inflorescence few spikeleted to many spikeleted (?); paniculate; not deciduous; open, or contracted (usually); with capillary branchlets, or without capillary branchlets (?); espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 15.2–50 mm long (always more than 15 mm); not noticeably compressed (?); disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present. The callus hairs white, or brown. Callus long (2.5–7 mm long); sharp pointed.
Glumes two; very unequal to more or less equal; about equalling the spikelets to exceeding the spikelets (?); nearly always long relative to the adjacent lemmas (?); pointed (lanceolate, long-acuminate); awned, or awnless (?); similar (lanceolate). Lower glume 1–4 nerved (? - evident). Upper glume 3–6 nerved (?). Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas narrowly cylindrical; not convolute (the margins tightly involute, not overlapping); not saccate; with an apical crown; decidedly firmer than the glumes; smooth (lacking abaxial-epidermal silica bodies); becoming indurated (horny); white in fruit to yellow in fruit (or cream); entire (the upper portion fused, without lobes); awned. Awns 1; median; apical; geniculate (bigeniculate); hairless, or hairy (but not long-plumose); much longer than the body of the lemma (50–200 mm long); entered by several veins (?); persistent. Lemmas sparsely hairy; non-carinate (terete); having the margins inrolled against the palea (the median zone of the palea exposed); without a germination flap; 3–7 nerved (?). Palea present; relatively long (subequal to the lemma); tightly clasped by the lemma; prow-tipped; awnless, without apical setae; thinner than the lemma, or textured like the lemma (?); indurated (more or less, at least the exposed part); 2-nerved (the veins extending to the apex); keel-less. Palea back glabrous (often), or scabrous, or hairy (?). Lodicules present; 3 (???); free; membranous (? stipoid); glabrous; not toothed. Stamens 3 (often short). Anthers 1.2–9 mm long (?); not penicillate. Ovary glabrous. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small, or medium sized, or large (?); fusiform; compressed laterally, or not noticeably compressed (?). Hilum long-linear. Embryo small; not waisted. Endosperm hard; without lipid; containing only simple starch grains, or containing compound starch grains (?). Embryo with an epiblast (the epiblast long and apically notched); without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Seedling with a short mesocotyl, or with a long mesocotyl (?). First seedling leaf with a well-developed lamina. The lamina narrow; erect; 3–5 veined (?).
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally to markedly different in shape costally and intercostally (the costals narrower); of similar wall thickness costally and intercostally (fairly thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (conspicuously pitted). Microhairs absent. Stomata common. Subsidiaries non-papillate; broadly parallel-sided to dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs and not paired (many solitary); silicified. Intercostal silica bodies imperfectly developed to present and perfectly developed; irregularly rounded to crescentic. Exhibiting numerous small prickles costally and intercostally. Costal short-cells predominantly paired. Costal silica bodies present and well developed to poorly developed; present throughout the costal zones; irregularly, imperfectly rounded, tall-and-narrow, and crescentic.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with radiate chlorenchyma to with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs; with the ribs very irregular in sizes (alternately large and small). Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (these small, in the bases of the furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma (except ajoining the blade margins). Combined sclerenchyma girders present; forming figures (the large bundles with Is, most of the small ones with anchors, Is or Ts). Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Cytology. Nucleoli disappearing before metaphase (?).
Taxonomy. Stipoideae; Stipeae.
Distribution, ecology, phytogeography. 5 species; North America. Commonly adventive (?). Mesophytic to xerophytic; species of open habitats. Seasonally dry grasslands.
Holarctic and Neotropical (?). Boreal. Atlantic North American and Rocky Mountains. Canadian-Appalachian, Southern Atlantic North American, and Central Grasslands (?).
Rusts and smuts. Rusts Puccinia. Smuts from Tilletiaceae and from Ustilaginaceae (?).
Economic importance. Significant weed species: the pointed calluses of S. comata and S. spartea sometimes injure livestock.
References, etc. Morphological/taxonomic: Barkworth and Everett 1987; Barkworth 1993. Leaf anatomical: this project - for H. comata only.
Special comments. This is a currently inadequate description of a Stipa segregate, consisting of S. comata, S. curtiseta, S. neomexicana and S. spartea. See further comment under Stipa sensu lato. Fruit data wanting.
Illustrations. • Awn, transverse section (H. spartea). Stipa (Hesperostipa) spartea. Awn with three vascular bundles.
This description is offered for casual browsing only. We strongly advise against extracting comparative information from it. This is much more easily achieved using 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 specified attributes, summaries of attributes within groups of taxa, geographical distribution, classification, and species sampled for anatomy.
Cite this publication as: ‘Watson, L., 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: 18th December 2012. http://delta-intkey.com’.