Poa arachnifera |
Poa confinis |
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Texas bluegrass |
beach blue grass, coastal bluegrass, coastline blue grass |
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Habit | Plants perennial; loosely tufted, rhizomatous, rhizomes slender. | Plants perennial; densely to loosely tufted, rhizomatous and stoloniferous, rhizomes and stolons to 1 m, slender. |
Culms | 20-85 cm, erect, terete or weakly compressed; nodes terete, 0-1 exserted. |
7-30 (35) cm tall, 0.4-0.9 mm thick, slender, erect or the bases decumbent, terete or weakly compressed; nodes terete, 0-1 exserted. |
Sheaths | closed firmly for 1/7-1/3 their length, sometimes for a longer distance by a hyaline membrane, terete, smooth, glabrous, bases of basal sheaths glabrous; ligules 1-4 mm, smooth or scabrous; innovation blades 10-35 cm long, 1-3.5 mm wide; cauline blades 2-25 cm long, 1.5-4.5 mm wide, flat or folded, lax, both surfaces smooth or sparsely finely scabrous, glabrous, apices narrowly to broadly prow-shaped. |
closed for 1/3-2/3 their length, terete, smooth, glabrous, bases of basal sheaths glabrous, distal sheath lengths (1)1.4-4.5 times blade lengths; collars smooth, glabrous; ligules 0.5-1.5(2.2) mm, scabrous, truncate to acute; innovation blades adaxially moderately to densely scabrous or hispidulous on and between the veins; cauline blades slightly reduced in length distally, 0.5-1(1.5) mm wide, involute, thin to moderately thick, usually filiform, soft, abaxial surfaces smooth, adaxial surfaces sparsely scabrous on and between the veins, apices narrowly prow-shaped, flag leaf blades (0.5)1-5 cm. |
Basal branching | intra- and extravaginal. |
mainly intravaginal, some extravaginal. |
Panicles | 3-12(18) cm, erect, narrowly cylindrical, often interrupted or lobed, congested, with (70)100-200 spikelets; nodes with (2)3-7(9) branches; branches 1-3(5) cm, erect to slightly ascending, terete or weakly angled, sparsely to densely coarsely scabrous, with 8-30 spikelets. |
1-5(7) cm, erect, ovoid, fairly tightly to loosely contracted, congested or moderately congested, with fewer than 50 spikelets; nodes with 1-2 branches; branches 0.5-3 cm, erect to ascending, slightly lax, terete or angled, angles sparsely to densely scabrous, with 2-12 spikelets. |
Spikelets | 4-8(10) mm, sexually dimorphic, laterally compressed, pistillate spikelets larger, with fewer florets and more pubescence than the staminate spikelets; florets 2-10; rachilla internodes smooth. |
3-6(8) mm, lengths to 3 times widths, laterally compressed, compact, not sexually dimorphic; florets 2-5; rachilla internodes 0.8-1.1 mm, usually not readily visible from the sides, glabrous or sparsely puberulent. |
Glumes | unequal, distinctly keeled, keels and lateral veins scabrous; lower glumes 1-3-veined. |
slightly unequal, distinctly keeled, keels smooth or scabrous; lower glumes 2-4 mm, 1-3-veined, about 2/3 the length of the adjacent lemmas; upper glumes 2.9-5 mm; calluses usually diffusely webbed, hairs 1-2 mm, infrequently glabrous; lemmas 2.5-4(4.5) mm, lanceolate, distinctly keeled, moderately to densely finely scabrous, glabrous throughout or the keels and sometimes the marginal veins sparsely puberulent proximally, margins narrowly scarious, glabrous, apices acute; paleas subequal to the lemmas, keels scabrous, intercostal regions glabrous; anthers vestigial (0.1-0.2 mm) or 1.5-2 mm. |
Pistillate florets | calluses copiously 3-webbed, hairs 4-10 mm, mostly silky, plicate; lemmas 4.2-6.4 mm, lanceolate, 5-7 veined, distinctly keeled, glabrous, or the keels and marginal veins, sometimes also the lateral veins, densely long-villous, margins glabrous, apices acute; palea keels scabrous, glabrous or sometimes softly puberulent to long-villous at midlength. |
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Staminate florets | calluses glabrous or sparsely dorsally webbed, hairs plicate, rarely with additional webs under the marginal veins; lemmas 3.5-5 mm, lanceolate, distinctly keeled, keels and marginal veins sparsely short- to long-villous, margins glabrous, apices acute; palea keels scabrous, glabrous or softly puberulent to long-villous at midlength; anthers vestigial (0.1-0.2 mm) or 1.6-2.7 mm. |
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2n | = 42, ca. 54, 56, ca. 63, 84. |
= 42. |
Poa arachnifera |
Poa confinis |
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Distribution |
AL; AR; FL; GA; IL; KS; LA; MS; NC; NM; OK; SC; TN; TX
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CA; OR; WA; BC |
Discussion | Poa arachnifera grows on moist, sandy to rich, black bottomlands of the southern Great Plains. At one time it was cultivated for winter pasture in the southeastern United States. It is strictly dioecious, with a 1:1 ratio of staminate to pistillate plants among herbarium samples. The variable and high chromosome numbers suggest it may be apomictic, but the occurrence of equal numbers of staminate and pistillate individuals in populations seems to suggest that reproduction is primarily sexual. It is the only non-South American species in the section. Its closest relatives appear to be P. bonariensis (Lam.) Kunth and P. lanuginosa Poir. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Poa confinis grows on sandy beaches and forest margins of the west coast, a habitat that is being lost to invasion by exotic species and development. It is closely related to P. diaboli (see next), from which it differs by a suite of characters. The two species are ecologically and geographically distinct. Poa confinis differs from P. pratensis (p. 522) in having glabrous or sparsely hairy lemmas and diffusely webbed calluses. It is gynodioecious. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 24. | FNA vol. 24, p. 552. |
Parent taxa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Dioicopoa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Madropoa > subsect. Madropoa |
Sibling taxa | ||
Name authority | Torr. | Vasey |
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