Thrasyopsis L. Parodi
Habit, vegetative morphology. Perennial; caespitose. Culms herbaceous; unbranched above. Culm nodes hairy. Leaves mostly basal; non-auriculate. Leaf blades narrow; without cross venation; persistent; an unfringed membrane; not truncate; 1 mm long.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence a single spike, or of spicate main branches (with short plump spikes); digitate (the material of T. repanda seen having 1–2 spikes), or non-digitate (when consisting of only one spike). Primary inflorescence branches 1–2. Rachides flattened (broad and flat). Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund; biseriate; subsessile.
Female-fertile spikelets. Spikelets 4–5 mm long; compressed dorsiventrally; biconvex; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes present; two; more or less equal; long relative to the adjacent lemmas; lateral to the rachis; hairless; awnless; non-carinate; similar (herbaceous). Lower glume 6–7 nerved. Upper glume 9 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; male. The proximal lemmas awnless; 7–9 nerved; more or less equalling the female-fertile lemmas; less firm than the female-fertile lemmas (membranous, glabrous); not becoming indurated.
Female-fertile florets 1. Lemmas decidedly firmer than the glumes (rigid, shining); becoming indurated (thinly); entire; pointed; awnless; hairless (shiny); non-carinate; having the margins lying flat on the palea; inconspicuously 3 nerved. Palea present; relatively long (firm); 2-nerved; 2-keeled. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers not penicillate; without an apically prolonged connective (but the anthers divaricate). Ovary glabrous. Styles fused. Stigmas 2; dark.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae not over-arching the stomata; consisting of one oblique swelling per cell to consisting of one symmetrical projection per cell. Mid-intercostal long-cells having markedly sinuous walls. Microhairs present; panicoid-type; (33–)39–42 microns long; 5.4–6.6 microns wide at the septum. Microhair total length/width at septum 6.1–7. Microhair apical cells (15–)22.5–24(–26) microns long. Microhair apical cell/total length ratio 0.45–0.61. Stomata common; 24–28.5 microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Numerous cushion-based macrohairs present. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; cross shaped, butterfly shaped, dumb-bell shaped, and nodular (all forms often with points); sharp-pointed (with points on representatives of the various forms).
Transverse section of leaf blade, physiology. C4; XyMS–. Mesophyll with radiate chlorenchyma. Leaf blade adaxially flat. Midrib conspicuous; having a conventional arc of bundles (3 large, 8 small bundles); with colourless mesophyll adaxially. Bulliforms in broad ‘fans’, extending all the way from one bundle to the next. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.
Taxonomy. Panicoideae; Panicodae; Paniceae.
Distribution, ecology, phytogeography. 2 species; Brazil. Savanna.
Neotropical. Central Brazilian and Pampas.
References, etc. Leaf anatomical: this project.
Special comments. Fruit data wanting.
Illustrations. • Transverse section of leaf blade
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).
