93. Cells irregularly globose or ovate, endophytic, buried within 



the tissues of higher aquatic plants. Chlorochytriwn 



93. Cells not endophytic 94 



94. Cells endozoic, inhabiting the tissues of sponges. Hydra, and 

 protozoa Zoochlorella 



94. Cells not endozoic - -95 



95. Cells epizoic, attached to small crustaceans such as Cladocera 



and copepods -96 



95. Cells not epizoic 98 



96. Cells fusiform or acicular, with a single diffuse chloroplast; 

 attached by a slender stipe.- Characium (inpartt 



96. Cells ovate or elliptic; chloroplast not a diffused sheet; attached 



by a thick stalk — -9 ' 



97. Cells with 1 or 2 laminate, elongate chloroplasts... ..C/iforangium (in part) 



97. Cells with many ovate, disc-like chloroplasts (usually in branched 

 colonies, sometimes solitary) .Colacium (in part) 



98. Cells free-living, not epiphytic or endophytic .—.100 



98. Cells epiphytic - --99 



99. Cells globose, gregarious, attached by the anterior end, which is 

 elongated to form a narrow stipe; with a massive chloroplast in 

 the upper (posterior) end of the cell; grovdng in the mucilage 



of blue-green algae -- Stylosj)haeridium 



99. Cells fusiform or cylindrical, attached to filamentous algae or 



higher aquatic plants Characium (in part) 



100. Cells fusiform to acicular, much longer than their diameter 101 



100. Cells not spindle-shaped but of various other forms: spherical, 



ovate, oblong, pyramidal, or polygonal 102 



101. Cells narrowly fusiform, 3-6/x in diameter, 50 (or more) times 



longer than wide - Closteriopsis 



101. Cells much smaller than above, length less than 25 times the 

 diameter An/cw<ro(fesmus ( in part ) 



102. Cells spherical, inclosed in a wide, spindle-shaped, 2-part enve- 

 lope (the parts adjoined at the equatorial plane) Desmatractum 



102. Cells not inclosed in a spindle-shaped envelope 103 



103. Cells spherical, wall decorated with a reticulum of ridges which 



form blunt or sharply pointed projections at the periphery Trochiscia 



103. Cells variously shaped; if spherical, without a reticulum 104 



104. Cells broadly and irregularly ellipsoid or subspherical, with 



thick uneven stratified walls ..- Excentrosphaera 



104. Cells spherical or of other shapes, without thick stratified walls 105 



105. Cells spherical - 1^^ 



105. Cells not spherical ^ 



106. Cells containing a single axial, stellate chloroplast with radiating 

 processes which become flattened at the periphery 



of the cell - ...Asterococcus (in part) 



106. Cells not containing a stellate chloroplast 107 



107. Cells large (50-300/^ in diameter), globular, containing numer- 

 ous ovate or disc-like chloroplasts arranged in radiating cyto- 

 plasmic strands and in a layer about the wall; chloroplasts shifting 



their position in response to light intensity Eremosphaera 



107. Cells smaller, without numerous ovate chloroplasts 108 



[579] 



