lateral walls where the cells adjoin at their 'bases'; cells 3-7/x in 

 diameter, 5-10/x long; colony 6-12.5yLi wide, 9-18/i, long. 

 Euplankter. Mich., Wis. 



Crucigenia crucifera ( Wolle) Collins 1909, p. 170 

 PL 65, Fig. 4 



Colony consisting of 4-sided cells arranged about a central square 

 opening, the outer free walls longer and concave, the outer free 

 angles of the cells rounded, the lateral adjoined walls straight and 

 converging inward where they adjoin other cells, the inner walls 

 about the central opening forming a short, straight side; multiple 

 colonies resulting from the adherence of quartets of cells by per- 

 sisting mother cell walls; cells 3.5-5/x in diameter, 5-7 ix long; colony 

 Q-llfx wide, 14-16/x long. 



Plankter. Mich., Wis. 



Crucigenia fenestrata Schmidle 1901, p. 234 

 PI. 65, Fig. 5 

 Colony consisting of 4 trapezoidal cells arranged about a square 

 opening, the outer free wall longest and convex, the free angles 

 sharply rounded; lateral and inner (the shortest) walls straight; 

 cells 3-5/x in diameter, 5-13/^ long; colony 8-14/^ wide, frequently 

 adjoined in closely arranged association to form multiple colonies. 

 Rare; found in the euplankton of a few lakes. Mich., Wis. 



Crucigenia irregularis Wille 1898, p. 302 

 PI. 65, Fig. 6 



Colony free-floating, consisting of 4, or multiples of 4 ovate cells 

 not definitely arranged about a central space as in other species of 

 the genus and not in quadrangular formation, with both lateral 

 and apical walls in contact; chloroplasts broad parietal plates or 

 discs, as many as 4 in a cell; pyrenoid sometimes absent; cells 5-9/x 

 in diameter, 8-14/x long. 



This is the most frequently seen species of Crucigenia in our 

 collections. It should be compared with C. rectangularis (Naeg.) 

 Gay which also has ovate cells but in which the cells have a 

 regular arrangement about a central space. 



Common in a large number of lakes and ponds. Mich., Wis. 



Crucigenia Lauterbornii Schmidle 1901, p. 234 

 PI. 65, Fig. 11 

 Colony free-floating, consisting of 4 subspherical cells arranged 

 in 2 opposite pairs about a large square space bounded by the flat, 



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