| 54a | Alga is a large seaweed growing in saline or slightly dilute saline waters of an estuary, shoreline fishpond, or lagoon. Somewhat firm in texture and parts are cartilaginous, although overall thallus may be stiff or lax | [59] | |||
| 54b | Thallus small, appearing filamentous: { usually less than a few cm long, or very thin and stringy. Alga growing in flowing, fresh water of a stream | [55] | |||
| 54c | Thallus encrusting: { thin, dark paint-like growth on smooth rocks in fast moving water | [34] | |||
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| 55a | (37) & (54) |
Main axis multicellular: consisting of a core of large axial cells covered by a layer of much smaller, cortical (surface) cells. Uniseriate (single celled) branches tapering. Swift flowing waters ~ Order COMPSOPOGONALES Compsopogon coeruleus
Compsopogon sp. |
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| 55b | Main axis filamentous and uniseriate (comprised of only single cells attached end on end) | [56] | |||
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| 56a | (55) |
Central axis conspicuous, bearing at regular intervals whorls of short, lateral branches. { Thallus enclosed in soft mucilage. Swift flowing water ~ Family BATRACHOSPERMACEAE Batrachospermum spermatiophorum
Batrachospermum spp. |
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| 56b | Main axis obscure (lateral branches tend to equal or exceed it in length) | [57] | |||
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| 57a | (56) |
Filaments rather stiff and branching, the branches arising at an angle <25o to main stem. Reproduction by rounded spores (monospores) forming at the tips of branches. { Usually forming short, dense tufts in swift-flowing water ~ Family ACROCHAETIACEAE |
[58] | ||
| 57b | Not as above | [65] | |||
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| 58a | (57) |
Color bluish. Monosporangia obovoidal or elliptical, 12.5-17.5 um long and 9.0 - 12.0 um diameter Audouinella pygmaea (Kutzing) Weber-van Bosse
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| 58b | Color reddish. Monosporangia >15.0 um long and >12.0 um in diameter Audouinella eugenea (Skuja) Jao
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| 59a | (54) | 
Plant with a single apical cell or central axial filament that is inconspicuous, lacking filamentous branches; main branches may be dichotomous, smaller branches arising irregularly; ends of branches pointed. { dark red to yellowish brown in color, lax but smooth and cartilaginous, often forming tangled clumps because of tendancy of longer branches to curve. Salinity range 18 - 36 ppt (tentative)
~ Order GIGARTINALES, Family HYPNEACEAE Hypnea cf. cervicornis J. Agardh
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| 59b | Plant with a single apical cell or central axial filament, with or without filamentous branches; if pointed branches present, then these short and stiff, spine-like ~ Order CERAMIALES |
[60] | |||
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| 60a | (59) |
Plant thallus bearing very short, simple or compound spine-like ultimate branches. { A moderately stiff, "crunchy" seaweed, yellowish or greenish brown in color, widespread, especially in the intertidal, and found in brackish fishponds ~ Family RHODOMELIACEAE Acanthophora spicifera (Vahl) Børgesen
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| 60b | Thallus of fully corticated axes, but ultimate branches uniseriate (filamentous), except for cortical bands. { Plant rather lax, bushy and fuzzy appearing, often whitish with accumulated silt. Common in shallow, confined waters of moderate salinity ~ Family CERAMIACEAE Spyridia filamentosa (Wulfen) Harvey
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