The grass genera of the world
Including Holboellia Hook.
Habit, vegetative morphology. Annual; caespitose. Culms 15–45 cm high; herbaceous; to 0.15 cm in diameter; unbranched above. Culm nodes glabrous. Plants unarmed. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; 3–6 mm wide; somewhat cordate (or amplexicaul); without abaxial multicellular glands; without cross venation; persistent. Ligule an unfringed membrane; 0.3–0.5 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence 5–10 cm long, cylindric, dense, ostensibly a false spike, with spikelets on contracted axes (best interpreted as a raceme of one-spikeleted racemelets); espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes very much reduced (to a short, cuneate rachis with one spikelet); solitary; disarticulating (interpreting the pedicel or callus as a reduced branch, which is shed); falling entire. Spikelets solitary; not secund (the racemelets spiralled); sessile.
Female-fertile spikelets. Spikelets unconventional (at least at first sight - of bizarre appearance, resembling a caricatured birds head in outline); about 2 mm long (excluding the 2 mm callus); compressed laterally; falling with the glumes (the disarticulation occurring at the base of a 1.5 mm hispidulous pedicel or callus, close to the main axis). Rachilla terminated by a female-fertile floret. Hairy callus present (i.e. the pedicel).
Glumes two; more or less equal (although the G1 is larger, enclosing the G2); long relative to the adjacent lemmas; hairy (with spicule-hairs on the keels); awnless; both strongly carinate; with the keel conspicuously winged; very dissimilar (both beak- shaped, the G1 leathery with globose base, narrow, and boat-shaped above, with a narrow, 2-lobed cartilaginous keel-wing having pectinate spinules, the G2 shorter and pectinate-keeled, only the upper half with a pectinate keel-wing). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only.
Female-fertile florets 1 (small). Lemmas rounded; saccate; less firm than the glumes (hyaline); not becoming indurated; entire; blunt; awnless; hairless; glabrous; non-carinate; having the margins lying flat on the palea; without a germination flap; 1 nerved. Palea present; relatively long; entire; awnless, without apical setae; not indurated (hyaline); 2-nerved (except at the base); 2-keeled. Lodicules absent. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (about 1 mm long, shaped like a birds head, hollowed above both hilum and embryo, curved and beaked above). Hilum short. Pericarp thin; fused. Embryo large. Endosperm hard.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals almost straight-walled); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; more or less spherical to elongated; clearly two-celled; chloridoid-type (the apical cells usually apiculate). Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 18–21 microns long. Microhair basal cells 9 microns long. Microhairs 6–6.6 microns wide at the septum. Microhair total length/width at septum 2.7–3.5. Microhair apical cells (7.5–)9 microns long. Microhair apical cell/total length ratio 0.43–0.5. Stomata common; 21–25.5 microns long. Subsidiaries triangular, or parallel-sided (in that the apices of the triangles are to varying extents truncated); including both triangular and parallel-sided forms on the same leaf. Guard-cells overlapped by the interstomatals (slightly). Intercostal short-cells absent or very rare. Intercostal silica bodies absent. Prickles absent. Crown cells absent. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; panicoid-type; cross shaped (a few), or dumb-bell shaped (mostly); not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions absent. Leaf blade adaxially flat. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; associated with colourless mesophyll cells to form deeply-penetrating fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent (seemingly abaxial girders only). Sclerenchyma all associated with vascular bundles.
Special diagnostic feature. Spikelets minute, shaped like cartoon birds heads.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Perotidinae. 1 species (L. ornithocephala Steud.).
Distribution, phytogeography, ecology. India, Ceylon.
Xerophytic; species of open habitats. Disturbed places in sandy ground: a sand stabilizer.
References, etc. Leaf anatomical: this project.
Illustrations. • L. ornithocephala, as Holboellia: W.J. Hooker (1831) Bot. Miscellany 2. • L. ornithocephala, abaxial epidermis of 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’.