Grass Genera of the World

L. Watson and M. J. Dallwitz


Gerritea Zuloaga & Morrone

Named for Gerrit Davidse, agrostologist.

Habit, vegetative morphology. Perennial; caespitose. Culms 20–100 cm high (procumbent, to 120 cm long); herbaceous; profusely branched above; many. Culm nodes hidden by leaf sheaths; hairy (pilose, with long whitish hairs). Culm internodes hollow. Young shoots intravaginal. Leaves not basally aggregated (mostly cauline); minutely auriculate; without auricular setae. Strongly keeled. Leaf blades linear-lanceolate; broad to narrow; 7–15 mm wide; flat; pseudopetiolate (attenuate to a 2 cm long pseudopetiole); without cross venation; disarticulating from the sheaths; a fringed membrane (abaxially pilose); truncate; 0.3–0.6 mm long.

Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality; hermaphrodite.

Inflorescence. Inflorescence many spikeleted; paniculate (terminal, exserted, lax, pyramindal); open (14–30 cm long, 4–12 cm wide with divergent first-order branches, the peduncle up to 10 cm long); with capillary branchlets (?); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelets solitary; not secund; long pedicellate (the pedicels flexuous, to 8 mm long).

Female-fertile spikelets. Spikelets 1.8–2.2 mm long (0.5 mm wide); elliptic; greenish or tinged with purple; slightly compressed laterally; falling with the glumes (?); disarticulating between the florets; with conventional internode spacings. The upper floret not stipitate. Rachilla terminated by a female-fertile floret. Hairy callus absent (?).

Glumes two; very unequal to more or less equal (subequal, or the lower somewhat shorter); long relative to the adjacent lemmas; hairy (with long, papillose-based hairs towards the margins); pointed (acuminate); awnless; non-carinate; very dissimilar to similar (the lower acuminate, the upper acute). Lower glume 0.75–1 times the length of the upper glume; longer than half length of lowest lemma; 3 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate. Palea of the proximal incomplete florets more or less fully developed (0.7–1 mm long, hyaline, 2 nerved). The proximal incomplete florets sterile. The proximal lemmas glumiform, acute; awnless; more or less equalling the female-fertile lemmas, or decidedly exceeding the female-fertile lemmas (?); similar in texture to the female-fertile lemmas (?); not becoming indurated.

Female-fertile florets 1. Lemmas narrowly ellipsoid; similar in texture to the glumes (? - ‘membranous’); smooth; not becoming indurated; ‘pale’; entire; pointed; awnless; hairless; glabrous; non-carinate; having the margins lying flat on the palea; 3 nerved. Palea present; relatively long; gaping (free of the lemma at the tip); awnless, without apical setae; not indurated; 2-nerved. Palea back glabrous. Lodicules present; 2; free; fleshy (‘truncate’); glabrous; not or scarcely vascularized. Stamens 3. Anthers 0.6–0.7 mm long; not penicillate; without an apically prolonged connective. Ovary glabrous. Styles free to their bases. Stigmas 2; white (‘whitish’).

Fruit, embryo and seedling. Disseminule unknown.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Intercostal zones with typical long-cells. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type (the distal cells sharply pointed); 70–98 microns long. Stomata common; 26–32.5 microns long. Subsidiaries non-papillate; triangular. Intercostal short-cells common (irregularly dispersed); in cork/silica-cell pairs and not paired (solitary and paired); silicified. Intercostal silica bodies cross-shaped (or irregular). Small hooks and macrohairs present. Costal short-cells conspicuously in long rows. Costal silica bodies present and well developed; ‘panicoid-type’; dumb-bell shaped.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with radiate chlorenchyma; more or less Isachne-type. Leaf blade slightly ‘nodular’ in section; with the ribs more or less constant in size (low round topped). Midrib conspicuous (by the large median bundle and keel); with one bundle only, or having a conventional arc of bundles (sometimes with two small laterals). The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups (in each furrow); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming ‘figures’ (anchors). Sclerenchyma all associated with vascular bundles.

Taxonomy. Panicoideae; Panicodae; Paniceae.

Distribution, ecology, phytogeography. 1 species; La Paz, Bolivia. Mesophytic; shade species; glycophytic.

Neotropical. Andean.

References, etc. Morphological/taxonomic: Zuloaga and Morrone 1993. Leaf anatomical: Zuloaga and Morrone 1993.

Special comments. Fruit data wanting.


Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).

Index