Pascopyrum A. Löve
Sometimes referred to ‘Agropyron smithii’, Elymus, Elytrigia
Habit, vegetative morphology. Strongly glaucous perennial; rhizomatous. Culms 30–90 cm high; herbaceous; unbranched above. Leaves not basally aggregated; auriculate (slender, pointed, on some of the sheaths). Sheath margins free. Leaf blades narrow; 2–7 mm wide; flat, or rolled (stiff, involute when dry); without cross venation; persistent; an unfringed membrane; truncate; 1 mm long.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets; outbreeding.
Inflorescence. Inflorescence a single spike, or a false spike, with spikelets on contracted axes (erect, 7–15 cm long, the ‘clusters’ reduced to one or two spikelets per node); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary (at all nodes), or solitary and paired (with a few pairs at the middle nodes); not secund; distichous; sessile; imbricate (not pectinate).
Female-fertile spikelets. Spikelets mostly 15–25 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets.
Glumes two; more or less equal (to slightly unequal); shorter than the spikelets; long relative to the adjacent lemmas (the G2 generally equalling or exceeding the L1); lateral to the rachis; hairless; glabrous; pointed (tapering); not subulate (lanceolate and tapering, by contrast with those of Leymus -but subulate when dry); awned, or awnless (tapering into an acute or short-awned apex); non-carinate; similar (rigid, with scarious margins). Lower glume 3–7 nerved. Upper glume 3–7 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets without proximal incomplete florets.
Female-fertile florets 4–9. Lemmas similar in texture to the glumes (firm, pale); not becoming indurated; entire; pointed, or blunt; awnless, or mucronate, or awned. Awns when present, 1; median; apical; non-geniculate; much shorter than the body of the lemma; entered by several veins. Lemmas glabrous, or basally pubescent; non-carinate; without a germination flap; ‘obscurely nerved’; with the nerves confluent towards the tip. Palea present; relatively long; 2-nerved; 2-keeled. Palea back hairy (pubescent). Stamens 3. Anthers 4–6 mm long. Ovary without a conspicuous apical appendage. Styles free to their bases. Stigmas 2; white.
Abaxial leaf blade epidermis. Costal/intercostal zonation fairly conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (fairly thick walled, pitted). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs absent. Stomata common; (72–)75–81(–84) microns long. Subsidiaries low dome-shaped, or parallel-sided. Guard-cells overlapped by the interstomatals (slightly). Intercostal short-cells common; in cork/silica-cell pairs (and solitary); silicified (occasionally only). Intercostal silica bodies rounded and tall-and-narrow. Crown cells absent (from the material seen, though it shows a few crown cell-like prickles near the margins). Costal short-cells neither distinctly grouped into long rows nor predominantly paired (solitary, paired and a few threes). Costal silica bodies crescentic; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs; with the ribs very irregular in sizes (there being a decidedly smaller rib intercalated between the large, round-topped ones towards the margin on either side). Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (in the furrows); exclusively in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the main veins, the minor ones having small abaxial strands only); forming ‘figures’ (I’s to T’s in the main bundles). Sclerenchyma all associated with vascular bundles.
Phytochemistry. Tissues of the culm bases with little or no starch. Fructosans predominantly short-chain.
Cytology. Chromosome base number, x = 7. 2n = 56. 8 ploid. Nucleoli disappearing before metaphase.
Taxonomy. Pooideae; Triticodae; Triticeae.
Distribution, ecology, phytogeography. 1 species; North America. Mesophytic; halophytic (in heavy, saline-alkaline soils).
Holarctic. Boreal. Atlantic North American and Rocky Mountains. Central Grasslands.
References, etc. Morphological/taxonomic: Löve 1984. Leaf anatomical: this project.
Special comments. Fruit data wanting.
Illustrations. • Abaxial epidermis 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).
