43a	(37)	Thallus branched, somewhat irregularly, without a clear axis, branches arising often at right angles. Cells tending to barrel-shape and about 1.5 (1 to 2) times as long as their ~10 um diameter. Yellow brown, plate-like chloroplasts number 1 (to 3?) per cell. Streams ?Apistonema sp.
	43b		Either thallus unbranched, OR branches clearly of smaller diameter, OR branches generally tapering and otherwise not as above. Chloroplasts yellow-green	[44]
			~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	44a	(31) & (43)	Thallus an unbranched filament. Cell walls "H"-shaped, overlapping near middle of each cell. Chloroplasts yellow-green in color. Uncommon ~ Division XANTHOPHYTA ~ Class XANTHOPHYCEAE Tribonema sp.
	44b		Thallus a branched or unbranched filament. Cell walls not overlapping near middle of cell. Chloroplasts bright, grass green ~ Divisions CHLOROPHYTA & STREPTOPHYTA (in part)	[45]

GREEN ALGAE  Chlorobionta (in part)  The "green" algae have long been thought to be close relatives to the higher plants because plastids in the cells of these algae contain chlorophylls a and b like the higher "land" plants. However, research into cell ultrastructure and biochemistry suggests that the old grouping "green algae" or Chlorophyta actually includes two lineages: one comprising those algae closely related to higher plants (Orders Zygnematales and Charales) and the other encompassing most of the remaining microscopic green algae and green seaweeds. The latter are characterized by flagellated reproductive cells, the former by a lack of such cells and sexual reproduction by conjugation. However, it is easier to develop a field key disregarding these phylogenic differences. "Green" algae of one or the other group in fresh and brackish waters are readily separated from the other kinds of algae by their bright, grass green color. Beyond that, microscopic examination of cell structure, branching pattern, and chloroplast shape are usually necessary to establish family and genus; details of sexual reproduction may be necessary to identify specimens to species. A listing of green algae described or reported from non-marine, aquatic environments in Hawai'i is given elsewhere in CPIE.

	45a	(44)	Filamentous green alga without evidence of branching, except maybe rhizoidal growths from the basal or attachment cell, OR branching limited to first several cells above the basal (attachment) cell	[46]
	45b		Filamentous green alga which is unbranched, but filaments becoming multiseriate (more than one cell thick) in upper sections. { Loosely attached to rocks in streams ~ Family SCHIZOMERIDACEAE Schizomeris leibleinii
	45c		Filamentous green alga which is clearly branching, and branches not limited to the basal part	[51]
			~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	46a	(45)	The chloroplast(s) parietal (in outer part of cell, against inside surface of cell wall), elongate, and arranged in a spiral. Thallus filaments to 0.05 mm dia.; bright green. Common in freshwater streams and pools ~ Order ZYGNEMATALES ~ Family ZYGNEMATACEAE Spirogyra (7+ species)
	46b		Chloroplasts either axile (distributed throughout the cell) or parietal; if parietal, then not in a spiral shape	[47]
			~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	47a	(46)	Some cells with transverse striations at distal end. Basal cell an expanded holdfast. Chloroplasts a reticular network. { Filaments quite variable in diameter to 0.07 mm across, sometimes decreasing from base to tip ~ Family OEDOGONIACEAE Oedogonium crispum Oedogonium globosum Oedogonium undulatum Oedogonium sp.
	47b		No cells with one or more transverse striations at distal end. Basal cell absent, or present as an expanded disc or with rhizoidal growths	[48]
			~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	48a	(47)	Chloroplasts one or two per cell; plate-like, globose, stellate, or ribbon shaped. { Filaments usually unattached	[49]
	48b		Chloroplast reticular, filling much of the cell. { Filaments usually attached to a substratum ~ Family CLADOPHORACEAE	[54]
			~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	49a	(48)	Chloroplast of vegetative cells elongate, plate-like, extending length of cell, in some cases slightly twisted. Cross walls between cells lens-shaped. { Around edges of ponds and in slow-flowing sections of streams ~ Family ZYGNEMATACEAE Mougeotia capucina Mougeotia sp.
	49b		Chloroplast of vegetative cells shorter than cell, round, plate-like, or stellate	[50]
			~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	50a	(49)	Chloroplasts one per cell, round or plate-like, and parietal ~ Family KLEBSORMIDIACEAE Klebsormidium flaccidum Klebsormidium rivulare Klebsormidium subtile
	50b		Chloroplasts two per cell, stellate (star-shaped) ~ Family ZYGNEMATACEAE Zygnema spp.
			~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	51a	(45)	Cross-walls infrequent, cells multinuclear. Branches tending to arise at or near the distal end of long cells, with branch crosswall forming a short distance up the branch ~ Family CLADOPHORACEAE	[53]
	51b		Structure not as above	[52]
			~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	52a	(51)	Branching sparse or profuse, with branches tapering and diameter of most branch cells half or less than half that of main axial cells. ~ Family CHAETOPHORACEAE	[55]
	52b		Cells of branches only slightly smaller or not smaller than main axis cells	[60]
			Key to Family Cladophoraceae
	53a	(51)	Filaments with short, swollen and densely packed cells called akinetes present along filament and at filament tips. Fresh to slightly brackish pools in full sun Pithophora sp.
	53b		Structure similar, but without akinetes Cladophora (7+ species)
			~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	54a	(48)	Basal or sometimes other cells with short, rhizoidal (narrow, twisted, root-like) branches. Fresh or brackish water ~ Family CLADOPHORACEAE Rhizoclonium crassipellitum Rhizoclonium hieroglyphicum Rhizoclonium hookeri
	54b		Basal several cells giving rise to multiple filaments (i.e., branching) that are themselves unbranched. Fresh water; reported also from the backs of turtles ~ Family CLADOPHORACEAE Basicladia chelonum
			Key to Family Chaetophoraceae
	55a	(52)	Branching profuse, radiating outward from a common point and encased in soft mucilage; branches generally short and tapering, in some cases tapering down to long, multicellular hairs. { Forming small green globules in streams Chaetophora elegans
	55b		Branching regular, profuse or not. Filaments not encased in mucilage and macroscopic form therefore not globular but tufted or feathery	[56]
			~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	56a	(55)	Branching profuse; branches generally short and tapering. Chloroplast parietal, encircling cell in a band (especially main axis cells). Basal part of main axis may be multicellular. { Swift water in fast flowing streams Cloniophora macrocladia Cloniophora plumosa (Kutz.) Cloniophora spicata Cloniophora sp.
	56b		Branching alternate or opposite or rarely dichotomous, regular but not profuse. Branches only slightly smaller than main axis filament, and tapering down to a blunt point or to long, multicellular hairs. Chloroplast parietal, encircling cell in a band { Forming green to yellow-green tufts in streams Stigeoclonium (13+ species)

	© 2006 AECOS, Inc. [FILE: algae3.html]		Green Algae
	INSTRUCTIONS   INDEX   REFERENCES	14