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The grass genera of the world

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

Peridictyon O. Seberg, S. Frederiksen & C. Baden

From the Greek peri- (around) and dictyon (a net), alluding to ‘netlike withering of the basal leaf sheaths’.

~ Festucopsis sancta (Janka) Meld.

Habit, vegetative morphology. Perennial; loosely caespitose. Culms (37–)47–80(–110) cm high; unbranched above; 2–3 noded. Culm nodes glabrous. Young shoots intravaginal. Leaves auriculate (the auricles (0.1-)0.3–0.7(-0.8) mm long). Sheath margins joined (the innovation leaves), or free. The basal sheaths disintegrating into a brownish mass of reticulate fibres. Leaf blades linear; narrow; (1–)1.6–2.6(–3.1) mm wide; not setaceous (junciform); rolled; not pseudopetiolate; disarticulating from the sheaths (‘with an abscission layer at junction of sheath and blade’). Ligule an unfringed membrane; truncate; ‘extremely short’.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.

Inflorescence. Inflorescence rather few spikeleted ((6-)7–13(-15)); a single spike ((5-)8–14(-17 cm long). Rachides flattened. Inflorescence espatheate. Spikelet-bearing axes persistent (?). Spikelets solitary; not secund; distichous (?); sessile.

Female-fertile spikelets. Spikelets (11–)12–19(–21) mm long; green; compressed laterally, or not noticeably compressed (?); disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret. Hairy callus absent. Callus very short.

Glumes two; more or less equal; shorter than the spikelets; shorter than the adjacent lemmas; hairless; glabrous; pointed; awned (the awn apical, 0.5–1.3 mm long); non-carinate; similar (lanceolate, leathery). Lower glume 2–4 nerved. Upper glume 3–6 nerved. Spikelets presumably with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped.

Female-fertile florets 5–10. Lemmas entire (?); awned. Awns 1; median; apical (?); non-geniculate; much shorter than the body of the lemma (3–9 mm long). Lemmas hairless; glabrous; non-carinate. Palea present; relatively long (equalling to slightly shorter than the lemma); 2-nerved; 2-keeled. Palea keels hairy (ciliate above). Lodicules present; 2; presumably membranous; ciliate. Stamens 3. Anthers 4.2–6(–6.3) mm long. Ovary apically hairy. Stigmas 2.

Fruit, embryo and seedling. Fruit adhering to lemma and/or palea (to the lemma); medium sized (4.5–5.5 mm long); with hairs confined to a terminal tuft. Hilum long-linear. Endosperm containing only simple starch grains.

Abaxial leaf blade epidermis. Costal/intercostal zonation lacking. Papillae absent. Long-cells similar in shape costally and intercostally (indistinguishable); of similar wall thickness costally and intercostally (thick walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (the sinuosity quite coarse, regular, associated with conspicuous pitting, and pits also conspicuous in the outside walls). Microhairs absent. Stomata absent or very rare. Intercostal short-cells absent or very rare; in cork/silica-cell pairs; silicified. Intercostal silica bodies rounded and crescentic. No macrohairs or prickles seen. Crown cells absent. Costal short-cells predominantly paired. Costal silica bodies present and well developed; rounded and crescentic.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size (broadly round topped). Midrib conspicuous (by the rather pointed abaxial keel, and its larger abaxial girder); with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups; in simple fans (these small-celled, in the furrows). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with the primaries, the minor bundles with small adaxial strands and abaxial strands or girders); forming ‘figures’ (the primaries with massive I’s). Sclerenchyma not all bundle-associated. The ‘extra’ sclerenchyma in a continuous abaxial layer (linking the abaxial sclerenchyma of the bundles).

Cytology. Chromosome base number, x = 7. 2n = 14. 2 ploid. Mean diploid 2c DNA value unknown, but chromosomes ‘large’.

Classification. Watson & Dallwitz (1994): Pooideae; Triticodae; Triticeae. Soreng et al. (2015): Pooideae; Triticodae; Triticeae; Hordeinae. 1 species.

Distribution, phytogeography, ecology. Greece and Bulgaria.

Species of open habitats; glycophytic. Calcareous, stony or rocky slopes.

References, etc. Morphological/taxonomic: Seberg et al. 1991. Leaf anatomical: this project.

Special comments. Morphological description scarcely adequate - e.g. spikelet orientation unknown. Fruit data wanting.


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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’.

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