The grass genera of the world
Habit, vegetative morphology. Perennial; caespitose. Culms 30–60 cm high; herbaceous; branched above; tuberous (the swellings associated with cleistogamous spikelets). Plants unarmed. Leaves not basally aggregated; non-auriculate. Sheaths pilose. Leaf blades linear; narrow; 3–7 mm wide; flat; exhibiting multicellular glands abaxially. The abaxial leaf blade glands intercostal (at the base of macrohairs). Leaf blades without cross venation; persistent. Ligule a fringed membrane, or a fringe of hairs (?).
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; exposed-cleistogamous, or chasmogamous; with hidden cleistogenes. The hidden cleistogenes in the leaf sheaths (one-flowered, in the basal sheaths).
Inflorescence. Inflorescence paniculate; open (rather loose, 8–15 cm long); espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 5–7 mm long; disarticulating above the glumes; disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus present. Callus short.
Glumes present; two; more or less equal; shorter than the spikelets; long relative to the adjacent lemmas (almost equalling them); hairy (pilose); acuminate or 3-toothed; awnless; similar (lanceolate). Lower glume 7–13 nerved. Upper glume 7–13 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped; awned to awnless.
Female-fertile florets 4–8. Lemmas not becoming indurated; incised; irregularly 9–11 lobed; deeply cleft; awned. Awns 9, or 11; median and lateral; the median similar in form to the laterals; non-geniculate; recurving (spreading); hairless to hairy; much shorter than the body of the lemma to much longer than the body of the lemma. The lateral awns shorter than the median and about equalling the median. Lemmas hairy (villous below); non-carinate (dorsally rounded); 9–13 nerved. Palea present; relatively long (somewhat longer than lemma); awnless, without apical setae; 2-nerved; 2-keeled. Palea keels hairy. Lodicules present; 2; joined to the palea; glabrous. Stamens 3. Ovary apically glabrous.
Fruit, embryo and seedling. Fruit small (0.75 mm long); ellipsoid; compressed dorsiventrally to not noticeably compressed. Hilum short. Pericarp fused. Embryo large; waisted; with an epiblast; with a scutellar tail; with an elongated mesocotyl internode; with one scutellum bundle. Embryonic leaf margins overlapping.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally (but the intercostals much larger); of similar wall thickness costally and intercostally (thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; Enneapogon-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs (138–)258–288(–300) microns long. Microhair basal cells 141–180 microns long. Microhairs (4.5–)10.5–12(–13.5) microns wide at the septum. Microhair total length/width at septum 22.2–30.7. Microhair apical cells (27–)42–48(–51) microns long. Microhair apical cell/total length ratio 0.14–0.19. Stomata common; (19.5–)21–24 microns long. Subsidiaries dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Intercostal silica bodies absent. Long macrohairs with basal rosettes present. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; panicoid-type; cross shaped (somu), or dumb-bell shaped (mostly).
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted both abaxially and adaxially. PCR sheath extensions absent. Leaf blade nodular in section to adaxially flat. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans (the large median cells deeply penetrating the mseophyll). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming figures (Is with all bundles). Sclerenchyma all associated with vascular bundles.
Special diagnostic feature. Female-fertile lemmas irregularly lobed, the lobes produced into 711 awns.
Cytology. Chromosome base number, x = 10. 2n = 20. 2 ploid.
Classification. Watson & Dallwitz (1994): Chloridoideae; Pappophoreae. Soreng et al. (2015): Chloridoideae; Eragrostideae; Cotteinae. 1 species.
Distribution, phytogeography, ecology. Texas to Argentina.
Xerophytic; species of open habitats.
References, etc. Leaf anatomical: this project.
Illustrations. • C. pappophoroides: Kunth (1835). • C. pappophoroides: Nicora & Rúgolo de Agrasar (1987). • C. pappophoroides, abaxial epidermis of leaf blade: this project. • C. pappophoroides, abaxial epidermis of leaf blade: this project. Showing the distal end of an Enneapogon type microhair - not to be confused with the macrohairs.
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’.