SCENEDESMUS. 173 



SCENEDESMUS DIMOKPHUS, Kg. 



Cells fusiform, acute, four to eight placed evenly in a 

 single row ; inner cells fusiform with ends often drawn out, 

 thin and long ; outer cells externally lunate. 



Syn. 8. bilunatus et geminatus. Kg. ; 8. pectinatus, Meyen ; Ach- 

 nanthes dimorpha, Turp. ; Arthrodesmus pectinatus, Ehrb. 

 Smaller stagnant pools. 



Plate CLVI, figs. 18-21, four forms. Sizes about the same 

 as the preceding species all are liable to some variation. 



SCENEDESMUS ACUTUS, Meyen. 



Cells fusiform, acute at each end, spineless, two to eight 

 united in a series, either single or double, straight and 

 irregularly alternately locked together. Three to six times 

 as long as wide. Transverse diameter of cells, 4-6 yw. 



Ponds and pools. 



Syn. 8. fusiformiSj Menegh. ; Arthrodesmus acutas, Ehrb. 

 Plate CLVI, figs. 25, 26, two series of cells. 



SCENEDESMUS OBTUSUS, Meyen. 



Cells oblong or ovate, obtuse at the ends, four to eight 

 loosely connected in a simple series, or two series side by 

 side, the thinner ends of the cells interlocking. Cells three 

 to five times as long as broad. 



Diameter of cells, 6-7 ^. 



Ponds and pools ; not as frequent as some of the other 

 forms. There is however a small form of cells, 6-7 n long, 

 in series of two to four or more, in basins of fountains, 

 which may belong here. These occur in quantity. 



Plate CLYI, fig. 22, the typical form; figs. 23, 24, the 

 forms from fountain basins. 



SCENEDESMUS POLYMOKPHUS, Wood. 



Cells fusiform, or oval or elliptic or globose, single or two 

 to seven conjoined, furnished in most cases with a single 

 spine, sometimes two at each end ; ends obtuse, subacute, 

 or very acute ; spines exceedingly slender and acute, straight, 

 moderately long, inclined. 



Diameter of cells, 4-12 yw. 



Dr. Wood remarks, "This plant was found in a quiet pool, 

 filling the water in such numbers as to make it opaque and 

 very green." 



To the present author this appears more like a hetero- 

 geneous mixture than a species. 



