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Published In: Variedades de Ciencias, Literatura y Artes 2(4,21): 134. 1805. (Varied. Ci.) Name publication detail
 

Project Name Data (Last Modified On 7/9/2009)
Acceptance : Accepted
Project Data     (Last Modified On 8/6/2009)

 

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36. Bouteloua Lag. (grama grass)

(Gould, 1979)

Plants perennial (annual elsewhere), with or without rhizomes. Flowering stems glabrous or minutely hairy at the nodes. Leaf sheaths rounded on the back, glabrous or hairy, the ligule a line or band of hairs. Leaf blades flat or with the margins inrolled. Inflorescences with 1–70 spikes, these arranged pinnately, all appearing lateral and spreading or angled downward. Spikes 0.8–4.0 cm long, with 2 to numerous spikelets, these loosely ascending (angled) in 2 rows along 1 side of the flattened axis, disarticulating above the glumes (leaving the axis of the spike appearing chaffy or scaly after the florets have been shed) or each of the spikes shed intact as a unit (leaving the unbranched, main axis of the inflorescence after the spikes have been shed). Spikelets with 1 perfect floret below usually 1 or 2 reduced, sterile florets. Glumes unequal in size and shape, the lower glume narrower and shorter than the upper glume, both 1‑nerved and sharply pointed at the tip, but usually unawned. Lemmas of fertile florets 3‑nerved, the tip with 3 teeth, the middle tooth usually short‑awned. Lemmas of sterile florets smaller than those of the fertile florets, but the awns usually longer, sometimes the floret reduced to a 3‑awned structure. Paleas of fertile florets 2‑keeled (absent in sterile florets). Fruits narrowly oblong‑elliptic. About 40 species, North America to South America, Caribbean Islands.

The species of Bouteloua fall into two very well separated subgenera. Bouteloua curtipendula belongs to the subgenus Bouteloua, which is characterized by inflorescences with relatively numerous spikes that are shed intact as individual units and 1–16 spikelets per spike. Bouteloua gracilis and B. hirsuta belong to the subgenus Chondrosum (Desv.) Gould, which differs in having inflorescences with relatively few spikes that are persistent on the main axis, with the mostly 20–60 spikelets per spike disarticulating above the glumes. Several members of subgenus Chondrosum are important components of shortgrass prairie and other arid grassland communities in the western United States. These two groups are treated as distinct genera by some authors (Clayton, 1982; Clayton and Renvoize, 1986; Pohl, 1994), but the presence of a few species with somewhat intermediate morphology has slowed the acceptance of this interpretation.

The cytological situation in Bouteloua is complicated by polyploidy and aneuploidy, and a long series of chromosome counts has been reported for most species. In the treatment below, the range of counts for each taxon is listed, along with the most commonly reported number(s).

 

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1 Inflorescences with (10–)30–70 spikes, these shed intact as a unit, leaving the main axis of the inflorescence naked after the spikelets have been shed; spikelets 2–8 per spike; leaf blades (2)3–7 mm wide 1 Bouteloua curtipendula var. curtipendula
+ Inflorescences with 1–4 spikes, these with a persistent axis, the spikelets disarticulating above the glumes, leaving the axis of the spike appearing chaffy or scaly after the florets have been shed; spikelets 20–60 per spike; leaf blades 1–3 mm wide (2)
2 (1) Axis of the spike not extended past the uppermost spikelet; upper glume sparsely hairy along the midnerve 2 Bouteloua gracilis
+ Axis of the spike extended 4–10 mm past the uppermost spikelet as a stiff, hairlike projection; upper glume densely hairy along the midnerve 3 Bouteloua hirsuta var. hirsuta
 
 
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