The grass genera of the world
~ Stipa sensu lato
Excluding Achnatherum, Anemanthele, Austrostipa, Hesperostipa, Lorenzochloa, Nassella, Orthachne, Ptilagrostis, Trikeraia
Habit, vegetative morphology. Perennial; densely caespitose. Culms (8–)10–90(–100) cm high; herbaceous; branched above, or unbranched above. The branching simple (nearly always), or suffrutescent, or fastigiate (more or less suffrutescent to fastigiate in S. muelleri). Culms 2–4 noded. Culm nodes exposed; hairy, or glabrous. Culm internodes solid (rarely), or hollow. Young shoots intravaginal. Leaves mostly basal, or not basally aggregated; auriculate, or non-auriculate. Leaf blades greatly reduced (occasionally), or not all greatly reduced (usually); linear; narrow; 0.3–4 mm wide; setaceous (e.g. S. tirsa), or not setaceous; flat (e.g. S. sibirica), or folded, or rolled, or acicular; without cross venation; persistent; rolled in bud, or once-folded in bud (?). Ligule an unfringed membrane, or a fringed membrane; truncate, or not truncate; 0.1–8(–15) mm long. Contra-ligule present, or absent (?).
Reproductive organization. Plants bisexual, all 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; paniculate; not deciduous; open, or contracted (?); 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 (10–)12–60(–90) mm long; compressed laterally, or compressed laterally to not noticeably compressed; disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present. The callus hairs white (at least in Section Stipa). Callus long ((1.2-)2–5 mm long); pointed.
Glumes two; very unequal to more or less equal (?); about equalling the spikelets to exceeding the spikelets (?); long relative to the adjacent lemmas; pointed; awned (usually, via long-acuminate apices), or awnless (?); similar. Lower glume 3 nerved, or 5(–7) nerved. Upper glume 3 nerved, or 5 nerved, or 7 nerved, or 9 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas lanceolate, (6.5-)10–30 mm long; convolute (covering the palea); not saccate; without a crown; decidedly firmer than the glumes; smooth (with the abaxial-epidermal silica bodies square or rectangular); becoming indurated to not becoming indurated (?); entire, or incised; when incised, usually minutely 2 lobed; deeply cleft (S. gigantea), or not deeply cleft; awned. Awns 1; median; from a sinus, or apical; geniculate (?); long-plumose; much longer than the body of the lemma (at least 10 cm and often over 30 cm long, up to 50 cm in S. pulcherrima); entered by several veins; persistent (but usually jointed at the base). Awn bases twisted. Lemmas hairy (the hairs usually ascending, diffuse or in longitudinal ranks); non-carinate (terete); having the margins lying flat on the palea; without a germination flap; 3–5 nerved. Palea present; relatively long (only slightly shorter than the lemma); tightly clasped by the lemma; not prow-tipped (flat); entire; awnless, without apical setae; thinner than the lemma; not indurated; 2-nerved (usually, the veins falling short of the apex), or several nerved (e.g. 2 strong and two weak veins in S. lingua); keel-less. Palea back glabrous, or scabrous, or hairy. Lodicules present; 3. Third lodicule present. Lodicules free; membranous (stipoid, the anterior usually somewhat different); glabrous (nearly always), or ciliate (e.g. S. margelanica); not toothed; heavily vascularized. Stamens 3. Anthers 2.5–10(–13) mm long; penicillate, or not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2, or 3–4 (3–4 in Section Barbata); white.
Fruit, embryo and seedling. Fruit free from both lemma and palea; medium sized to large (4–18 mm long); linear, or fusiform; not grooved; compressed laterally. 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 of S. pennata short and truncate); without a scutellar tail (with a 95–130 degree angle between coleoptile and coleorhiza); 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 lacking. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Intercostal zones with typical long-cells. Mid-intercostal long-cells rectangular; having markedly sinuous walls (heavily pitted). Microhairs absent (but sometimes recorded adaxially, then inconspicuous, flimsy, perhaps one-celled). Stomata absent or very rare. Intercostal short-cells common; in cork/silica-cell pairs (and some ostensibly solitary); silicified. Intercostal silica bodies present and perfectly developed; rounded, crescentic, and tall-and-narrow (not more than slightly crescentic). Prickles, sometimes blunt, and a few thick-walled macrohairs, in S. pennata. Costal short-cells predominantly paired. Costal silica bodies present and well developed; rounded, tall-and-narrow, and crescentic (S. pennata), or rounded and crescentic (S. tenacissima).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs; with the ribs very irregular in sizes. Midrib not readily distinguishable (other than by its position); with one bundle only; without colourless mesophyll adaxially. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups (S. pennata), or not present in discrete, regular adaxial groups (S. tenacissima); of S. pennata in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the larger bundles); forming figures. Sclerenchyma not all bundle-associated. The extra sclerenchyma in a continuous abaxial layer (joining the bundles).
Phytochemistry. Tissues of the culm bases with abundant starch. Leaves without flavonoid sulphates.
Cytology. Chromosome base number, x = 11, or 12. 2n = 36, or 40, or 44 (with 44 commonest). 3 ploid, or 4 ploid. Chromosomes small to medium sized. Nucleoli disappearing before metaphase (?).
Classification. Watson & Dallwitz (1994): Stipoideae; Stipeae. Soreng et al. (2015): Pooideae; Stipeae. About 50 species (?).
Distribution, phytogeography, ecology. Eurasia, Mediterranean, Africa (especially Near and Middle East).
Commonly adventive. Xerophytic; species of open habitats.
Economic aspects. Important native pasture species: many important in dry climates, e.g. S. barbata, S. lessingiana. S. tenacissima (Halfa, Esparto grass) used for papermaking mats and cordage.
Rusts and smuts. Rusts Puccinia. Smuts from Tilletiaceae and from Ustilaginaceae.
References, etc. Morphological/taxonomic: Tsvelev 1976; Barkworth and Everett 1987; Jacobs amd Everett 1996. Leaf anatomical: Metcalfe 1960.
Special comments. This is an unsatisfactory attempt to account for the proposed sensu stricto treatment of Stipa. Supposedly characteristic rectangular abaxial leaf blade epidermal silica bodies (Barkworth and Everett 1987) are refuted by Metcalfes detailed descriptions of two of the best known species. See further comment under Stipa sensu lato. Anatomical data more or less satisfactory (though limited to S. pennata and S. tenacissima).
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: 11th December 2017. delta-intkey.com/grass’.