Achnatherum diegoense |
Poaceae subfam. pooideae |
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San Diego County needlegrass, San Diego needlegrass |
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Habit | Plants cespitose, not rhizomatous. | Plants annual or perennial; sometimes matlike, sometimes cespitose, sometimes stoloniferous, sometimes rhizomatous. | ||||||||||||||||||||||||||||||||||||
Culms | 110-140 cm tall, 2.5-4 mm thick, internodes densely and retrorsely pubescent for 3-9 mm below the nodes, particularly the lower nodes, glabrous or retrorsely puberulent elsewhere; nodes 3, pubescent or glabrate. |
usually hollow, sometimes solid. |
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Leaves | distichous; sheaths usually open to the base, varying to closed for nearly their full length; auricles present or absent; abaxial ligules absent; adaxial ligules scarious or membranous, sometimes puberulent or scabridulous, usually not ciliate, cilia sometimes shorter than the base; pseudopetioles rarely present; blades usually linear, sometimes broadly so, venation parallel; cross sections non-Kranz, mesophyll nonradiate, adaxial palisade layer absent, fusoid and arm cells usually absent; midribs usually simple; adaxial bulliform cells present; stomates with parallel-sided subsidiary cells; epidermes usually lacking bicellular microhairs, sometimes with unicellular microhairs, papillae usually absent, when present, rarely more than 1 per cell. |
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Panicles | 21-25 cm long, (2)4-8 cm wide; branches strongly divergent to ascending, straight, lower branches 5-7 cm. |
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Inflorescences | usually terminal, panicles, spikes, or racemes, usually ebracteate; disarticulation usually below the florets, sometimes below the glumes, at the rachis nodes, or at the inflorescence bases. |
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Spikelets | appressed to the branches. |
usually bisexual, infrequently unisexual or mixed, usually laterally compressed or not compressed, occasionally dorsally compressed, with 1-30 sexual florets, distal floret(s) often reduced, infrequently spikelets with 1-2 reduced or staminate basal florets and a single terminal sexual floret. |
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Glumes | subequal, 8-11.5 mm; lower glumes 0.5-1 mm wide, 3-5-veined; upper glumes 3-veined; florets 5.5-7.5 mm long, 0.7-1 mm thick, fusiform, terete; calluses 0.25-1.2 mm, acute; lemmas evenly hairy, hairs at midlength and at the apices 0.5-1 mm, apical lobes 0.2-0.4 mm, membranous, flexible; awns 20-50 mm, persistent, twice-geniculate, all segments scabrous to scabridulous, terminal segment straight; paleas 2.6-3.8 mm, 1/2 - 3/4 as long as the lemmas, pubescent, hairs not extending beyond the apices, veins terminating below the apices, apices rounded; anthers 2.5-4 mm, dehiscent, not penicillate. |
usually 2, upper or lower glumes sometimes absent, rarely both glumes absent; lemmas without uncinate hairs, awned or not, awns single, basal to apical; paleas usually well-developed, sometimes reduced or absent; lodicules 2(3), usually lanceolate and broadly membranous distally, rarely truncate and fleshy, usually not veined or obscurely veined, sometimes distinctly veined, sometimes ciliate; anthers (1, 2)3; ovaries glabrous or sometimes hairy distally, sometimes with an apical appendage; haustorial synergids absent; styles (1)2 (-4), bases close together, sometimes fused. |
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Caryopses | hila linear, elliptic, ovate, or punctate; endosperm usually hard, sometimes soft or liquid, with or without lipids, starch grains compound or simple; embryos less than 1/2 the length of the caryopses; epiblasts usually present; scutellar cleft usually absent; mesocotyl internode usually absent; embryonic leaf margins overlapping, x = 7, 10. |
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Basal | sheaths mostly glabrous or puberulent, margins ciliate distally; collars glabrous or with hairs, hairs mostly to 0.5 mm, sides with tufts of 1.5-2 mm hairs; ligules 0.4-2 mm, rounded to acute, abaxial surfaces hairy, hairs to 0.5 mm; upper ligules 1-3 mm, similar in structure and pubescence; blades 1-3.5 mm wide, abaxial surfaces smooth or scabrous, adaxial surfaces prominently ribbed, hairy, hairs 2-3 mm. |
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2n | = unknown. |
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Achnatherum diegoense |
Poaceae subfam. pooideae |
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Distribution |
CA
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Discussion | Achnatherum diegoense grows in chaparral and coastal sage scrub, on rocky soil near streams or the coast, at 0-350 m, on the Channel Islands of Santa Barbara County, California, and, on the mainland, in Ventura and San Diego counties south into Baja California, Mexico. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
The subfamily Pooideae includes approximately 3300 species, making it the largest subfamily in the Poaceae. It reaches its greatest diversity in cool temperate and boreal regions, extending across the tropics only in high mountains. The circumscription and relationships of tribes within the Pooideae are unsettled (see, for example, Catalan et al. 1997, 2004; Soreng and Davis 1998). In this flora, some previously recognized tribes have been combined with the Poeae. Recognition of some of these as subtribes is well supported; among these is the Hainardieae Greuter (which, at the subtribal level, is called the Parapholiinae Caro). Members of other traditional tribal groupings, such as the Aveneae Dumort., appear to be widely dispersed within the Poeae sensu lato. Further work will probably support the division of the expanded Poeae into additional tribes; there is as yet no clear indication as to what the boundaries of such tribes should be. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 24, p. 131. | FNA vol. 24, p. 57. | ||||||||||||||||||||||||||||||||||||
Parent taxa | Poaceae > subfam. Pooideae > tribe Stipeae > Achnatherum | Poaceae | ||||||||||||||||||||||||||||||||||||
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Name authority | (Swallen) Barkworth | Benth. | ||||||||||||||||||||||||||||||||||||
Web links |