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CPIE Notebook Project - Grasses of Hawai‘i and Guam Grass Key – Page 17

  Our most common open panicle grasses with the inflorescence NOT ovoid in overall shape is:
  • Sourgrass
[PANICULATE INFLORESCENCES CONTINUED]

     
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100a (To last page81) Spikelet with one or more conspicuous awns greater than length of spikelet [101]
100b

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

[105]
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101a (100 & To ptrvious page36) 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. .. . [102]
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.

[103]
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102a (101) Magnifying Lens Awns clearly twisted at base. Glumes equal or nearly so. Poverty threeawn [HAW - ?NAT]
    Aristida divaricata Humb, & Bonpl. ex Willd.
102b Awns not twisted at base. Glumes not equal. { Small, usually annual, clumping grass common on exposed soils in dry areas, such as around Waikoloa Village on Hawai‘i (Fig. 17B). Sixweek threeawn [HAW - NAT]
    Aristida adscensionis L.
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103a (101) Spikelets more or less fusiform in shape, pubescent to some degree. Dense ring of long or short hairs at culm nodes. Ligule a membrane with or without a ciliate margin [104]
103b

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 [HAW - NAT]

    Echinochloa crus-galli (L.) P. Beauv.
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104a (103) Some secondary branching of panicle. Spikelets along rachis occur pairs: one sesile and one pedicillate. Racemes with more than 8 spikelets .. . [110]
104b

Lower leaf sheaths silky; culm nodes pubescent. Panicle with many secondary branches. Terminal racemes three: one sesile and two pedicillate. Racemes with 3 to 7 spikelets, sessile spikelets 3-4 mm long (pedicelled spikelets usually shorter). { Rare on O‘ahu, medium-sized, tufted perennial. [HAW - NAT]

    Capillipedium spicigerum S. T. Blake
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105a (100) Inflorescence of tightly clustered (aggregated) spikelets forming lobes; initial branching more or less in one plane. Compressed spikelets on the order of 8 mm (1/3 in) in length. Glumes and lemmas spine-tipped (short-awned). Culms laterally compressed. { Medium to large, coarse, tufted perennial. Cocksfoot [HAW - NAT]
    Dactylis glomerata L.

105b Grass is otherwise

[106]

SUPPLEMENTAL PHOTOS
[CLICK ON THUMBNAIL TO OPEN AN ENLARGED IMAGE]
Aristida adscensionis habit Pitted beardgrass showing pits

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



Fig. 17C. Closeup of pitted beardgrass (Bothriochloa pertusa) spikelets showing distinctive pits
(0.24 MB).



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Open Panicle Grasses – Page 17

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