195

1.	Frond a single cell (its division being followed by separation), or cells fasciculated	2
	Frond composed of several cells	13
2.	Segments, in the front view of the frond, lobed, incised, sinuated, or notched	3
	Segments, in the front view, undivided	4
3.	Frond fusiform; segments notched at the end, otherwise entire.	Tetmemorus - key
	Frond oblong, compressed; segments sinuated	Euastrum - key
	Frond lenticular; lobes of segments incised or bidentate at the apex	Micrasterias - key
4.	End view of frond angular or radiate	5
	End view of frond neither angular nor radiate	6
5.	Processes geminate from each angle, one external to the other	Didymocladon - key
	Processes, if present, with their divisions on the same plane	Staurastrum - key
6.	Cells short, rarely more than twice as long as broad	7
	Cells elongated (cylindrical, fusiform or lunately curved)	9
7.	Frond with elongated, simple or branched spines	8
	Frond not spinous	Cosmarium - key
8.	Segments with two spines	Arthrodesmus - key
	Segments with four or more spines	Xanthidium - key
9.	Cells straight	10
	Cells curved	12
10.	Endochrome spiral	Spirotaenia - key
	Endochrome not spiral	11
11.	Frond moderately elongated, if linear not constricted at the middle, and its segments not inflated at the base	Penium - key
	Frond much elongated, linear, generally much constricted at the middle, and its segments inflated at the base	Docidium - key
12.	Cells not fasciculated	Closterium - key
	Cells fasciculated	Ankistrodesmus - key
13.	Frond an elongated jointed filament	14
	Frond of few cells not forming a filament	18
14.	Filament plane or triangular, with junction-glands or foramina between the joints	15
	Filament never plane; neither glands nor foramina between the joints	16
15.	Joints with junction-glands; their margins incised or sinuated	Sphaerozosma. - key
	Joints with foramina between them; their margins bicrenate or entire	Aptogonum - key
16.	Filament triangular or quadrangular	Desmidium - key
	Filament cylindrical or subcylindrical	17
17.	Joints surrounded by a groove	Hyalotheca. - key
	Joints with two opposite bicrenate projections	Didymoprium. - key
18.	Cells arranged in the form of a flattened star	Pediastrum. - key
	Cells placed side by side in one or two rows	Scenedesmus. - key