The grass genera of the world
~ Bouteloua sensu lato
Including Bulbilis Raf., Calanthera Hook., Lasiostega Benth.
Habit, vegetative morphology. Grey-green, low, dense turf-forming perennial; stoloniferous. Culms 1–30 cm high; herbaceous; unbranched above. Culm internodes solid. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; 1–2 mm wide (sparsely pilose); without abaxial multicellular glands; without cross venation; rolled in bud. Ligule a fringe of hairs; 0.5 mm long.
Reproductive organization. Plants monoecious with all the fertile spikelets unisexual (occasionally), or dioecious; without hermaphrodite florets. The spikelets of sexually distinct forms on the same plant, or all alike in sexuality; female-only, or male-only. The male and female-fertile spikelets in different inflorescences. Plants outbreeding (at least, when dioecious).
Inflorescence. Inflorescence when male elevated, with 1–4 spicate, unilateral branches 6–14 mm long; when female with spikelets in burr-like clusters of 3–5(-7), usually 2 burrs per inflorescence, the burr on a short, stout rachis, partially enclosed in a broad, bracteate leaf sheath, falling entire with the indurate rachis united to the indurate G2s; spatheate (female inflorescences more or less hidden among culm leaves), or espatheate (male inflorescences); a complex of partial inflorescences and intervening foliar organs (female inflorescence), or not comprising partial inflorescences and foliar organs (male inflorescence). Spikelet-bearing axes of female inflorescences capitate; those of female plants disarticulating; falling entire. Spikelets secund (male spikelets in two rows on one side of rachis), or not secund (female spikelets in burrs).
Female-sterile spikelets. Male spikelets with 2 fertile florets, the lemmas 3-nerved, the lodicules 2, fleshy, heavily vascularised. The male spikelets with glumes (two, similar, of variable relative lengths, sometimes mucronate); 2 floreted.
Female-fertile spikelets. Spikelets adaxial; compressed dorsiventrally; falling with the glumes (the burrs falling entire), or not disarticulating. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; very unequal; (the longer) long relative to the adjacent lemmas; free (of one another); hairless; awnless; non-carinate; very dissimilar (G1 narrow, thin, mucronate, well developed to obsolete, G2 firm, thick, expanded in the middle with inflexed margins, enveloping the floret, abruptly contracted above, the apex with 3 rigid acuminate lobes). Spikelets with female-fertile florets only.
Female-fertile florets 1. Lemmas less firm than the glumes (firmly membranous); not becoming indurated; incised; 3 lobed (the middle lobe larger); the lobes mucronate; hairless; non-carinate (dorsally compressed); 3 nerved. Palea present; about equalling body of female-fertile lemma; 2-nerved. Lodicules present (reduced), or absent; when present, 2; membranous. Ovary apically glabrous. Stigmas 2; brown.
Fruit, embryo and seedling. Fruit free from both lemma and palea; ellipsoid. Hilum short. Pericarp fused. Embryo large; with an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells rectangular; having markedly sinuous walls (the sinuosity small-scale). Microhairs present; elongated; clearly two-celled; chloridoid-type (with elongated basal cells). Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs (34–)40–55(–75) microns long. Microhair basal cells 54 microns long. Microhairs 10.5–15 microns wide at the septum. Microhair total length/width at septum 4.25–5.1. Microhair apical cells (10.5–)12–21(–29) microns long. Microhair apical cell/total length ratio 0.21–0.39. Stomata common; 21–24 microns long. Subsidiaries slightly triangular, or dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs and not paired (some solitary); silicified. Intercostal silica bodies imperfectly developed; tall-and-narrow. Costal short-cells conspicuously in long rows (in some files), or predominantly paired (in others), or neither distinctly grouped into long rows nor predominantly paired (in a few places). Costal silica bodies present in alternate cell files of the costal zones; large, saddle shaped.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; biochemical type NADME (B. dactyloides); XyMS+. PCR sheath outlines even. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only, or interrupted both abaxially and adaxially. PCR sheath extensions absent. PCR cells without a suberised lamella. PCR cell chloroplasts with well developed grana; centripetal. Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells. Leaf blade with distinct, prominent adaxial ribs (slight), or adaxially flat; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans and associated with colourless mesophyll cells to form deeply-penetrating fans (the latter groups contributing to the colourless columns). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres (few cells).
Phytochemistry. Tissues of the culm bases with abundant starch.
Special diagnostic feature. The male inflorescences elevated, with one to four spicate, unilateral branches; female spikelets in burr-like clusters, usually two burrs per inflorescence, each burr on a short, stout rachis, partially enclosed in a broad, bractlike leaf sheath, falling entire with the indurate rachis united with the upper glumes.
Cytology. Chromosome base number, x = 10. 2n = 20, 40, 56, and 60. 2, 4, and 6 ploid.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Boutelouinae (as a synonym of Bouteloua). 1 species.
Distribution, phytogeography, ecology. North America.
Xerophytic; species of open habitats. Dry plains.
Economic aspects. Significant weed species: B. dactyloides. Cultivated fodder: B. dactyloides (Buffalo). Important native pasture species: B. dactyloides.
Rusts and smuts. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae Tilletia. Ustilaginaceae Ustilago.
References, etc. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • B. dactyloides: Hitchcock and Chase (1950). • Male spikelets (BuchloŽ dactyloides). • B. dactyloides, TS leaf blade: this project
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: 13th November 2017. delta-intkey.com/grass’.