CPIE Notebook Project - Key to Grasses of Hawai‘i

Page 17


Our most common open panicle grasses with the inflorescence NOT ovoid in overall shape are:

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100a (81) Spikelet with one or more conspicuous awns greater than length of spikelet [101]
100b

Spikelets without conspicuous awns; if present, awns not any longer than bracts to which they are attached

[110]
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101a (100) & 36 Magnifying Lens Awn arising from tip of spikelet is three parted (essentially, three awns arise from top of lemma). Spikelet long and narrow, longer than two glumes, which remain on pedicel after spikelet falls. { Small, usually annual, clumping grass common on exposed soils in dry areas, such as around Waikoloa Village on Hawai‘i. Sixweek threeawn. (Fig. 17A) [NAT]
Aristida adscensionis L.
101b

Awns not branched, one or two awns per spikelet. Inflorescence of several (typically 3-7) ascendent (pointed upwards), racemes, arranged fan-like (flabellate) or subdigitate on a tall, thin culm.

[102]
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102a (101) Spikelets more or less fusiform in shape, pubescent to some degree. [103]
102b

Spikelets subglobose, somewhat flattened on one side, apices pointed to awned, but awns vary between spikelets from shorter than spikelet to 10x longer or more. Hairs on glumes stiff and curved upwards. Spikelets arranged in 2 to several untidy rows along raceme. {Medium-sized, bunching grass, typically in wet areas and along waterways. Barnyard grass [NAT]

Echinochloa crus-galli (L.) P. Beauv.
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103a (102) Pubescence of rachis and glume margins of long hairs that almost obscure view of spikelets. Sessile spikelet of paired spikelets narrower than pedicelled (stalked) spikelet. Culm with a dense ring of long hairs (villous) at each exposed node; node may be dark purple in color. Ligule membranous. {Uncommon, medium-sized, tufted perennial. Fuzzy top. [NAT]
Bothriochloa barbinodis (Lag.) Herter

103b Pubescence of rachis and glumes of hairs shorter than glumes, these not at all obscuring view of spikelets. Sessile spikelet of paired spikelets about as broad as pedicelled spikelet.

[104]
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104a (103) Pitted beardgrass photo Magnifying Lens First glume with a distinct pit, visible to naked eye (if you have good eye-sight). Racemes subdigitate, or attached along central axis over a distance less than raceme length. {Extremely common small grass in lawns and along roads and other disturbed sites. Pitted beardgrass. [NAT]
Bothriochloa pertusa (L.) A. Camus

Figure 11A. Bothriochloa pertusa inflorescences with fan-shaped arrangement of racemes and (inset) glumes with a small pit (clearly visible with a small hand lens).

104b

First glume lacking a pit. Racemes attached along central axis over a distance greater than raceme length. Pedicels especially with many long hairs. {Uncommon, medium-size, bunching grass, typically in disturbed sites. [NAT]

Bothriochloa bladhii (Retz.) S. T. Blake
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110a (100) Inflorescence of tightly clustered (aggregated) spikelets forming lobes; initial branching more or less in one plane. Lemmas short-awned. Culms laterally compressed. {Somewhat uncommon, medium to large, coarse, tufted perennial. Cocksfoot. [NAT]
Dactylis glomerata L.

110b Grass otherwise

[111]

 

SUPPLEMENTAL PHOTOS
[CLICK ON THUMBNAIL TO OPEN AN ENLARGED IMAGE]
Aristida adscensionis habit

Fig. 17A. Habit of sixweek threeawn (Aristida adscencionis) showing the distinctive three-parted awns of the spikelets. (3.9 MB).


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