THE GREEN ALGAE OF NORTH AMERICA 47 



Var. WESTII G. M. Smith, igi6a, p. 480, PI. XXXIII, figs. 

 177-180. Cells 16-22 X 4.5-8 p.; spines 12-16 ft long. Wis., 

 G. M. Smith. 



A large form, but in its maximum not reaching the minimum 

 of var. maximus. 



Var. MAXIMUS W. & G. S. West, 18953, p. 83, PI. V, figs. 

 9-10 ; G. M. Smith, 19163, p. 481, PI. XXVII, fig. 40. Cells 

 twice as large as in the typical form, 27-36 X 9-11.4 /*, with 

 long curved spines. Waltham, Mass., F. D. Lambert. 



Europe, Africa, Asia. 



17. S. OPOLIENSIS Richter, 1896, p. 7, fig. A-E ; G. M. 

 Smith, 19163, p. 481, PL XXVII, fig. 49; XXXII, figs. 181- 

 184. Colonies 2-4-celled, cells in a straight series, end cells 

 fusiform or subnavicular, with a long spine at each pole ; 

 median cells regularly fusiform, usually unarmed ; cells united 

 for about the median third only; cells 17-28 X 5-8 p. ; Lske 

 Erie, Snow; Wis., G. M. Smith. Europe. 



The chsracters just given are the normal for the species, but 

 there is much variation as to the size 3nd number of the spines ; 

 they are never entirely wanting, and on the other hand are 

 never present on all the poles in the colony. 



Page 170, for description of CRUCIGENIA, substitute. 



Colonies free, of 4-8-16, rarely more cells, lying in the same 

 plane, with perforations at places where the cells have divided 

 and separated from each other; cells with parietal chromato- 

 phore, with or without pyrenoid, touching at the middle or at 

 the edges, and enclosed in more or less plentiful gelatine ; asex- 

 ual reproduction by division of a cell into 4 daughter cells, 

 arranged like the mother colony. Fresh water plankton 3lg3e. 



KEY TO THE SPECIES OF CRUCIGENIA. 



i. Cells with more or less rounded outline. 4. 



i. Cells more distinctly angular. 2. 



2. Cells triangular. 6.. C. tetrapedia. 



2. Cells not triangular. 3. 



3. Cells rhomboidal, sides concave. 2. C. crucifera. 



3. Cells trapeziform. 7- C.fcnestrata. 



4. Cells quadrate with rounded corners, or suborbicular. 



3. C. quadrata. 



4. Cells oval, oblong or subtriangular. 5. 



5. Colonies of 4 cells, separating soon after division. 



i. C. rectangularis. 

 5. 4-celled colonies remaining united. 6. 



