3J. THE FLORA OF NEBRASKA. 



H. SCENEDESMUS Meyen Nov. Act Leop. XIV. 2, 774. 1829. 



Colony composed of 2-16 ovoid or fusiform oblong cells joined together in a 

 single row; propagation by the cell-contents breaking up into one or 

 more families which are set free by rupture of the mother-cell mem- 

 brane. 



Etymology: Greek ew/r//, stage, and dea/wc, chain. 



Section I.— Cells with both ends rounded. 



Scenedesmns bijugatns (Tubpin) Kuetz. Syn. Diat. GOT. 1831. 

 Scenedesmus dbtusus Meyen. 1. c. 775. 



Cells oblong or ovate, obtuse at the ends, 4-10 loosely connected in a simple 



or double series; cells 8-12x6-7 fi. 

 In stagnant water. PI. IV., Fig. 8. 



Scenedesmns quadrieauda (Tubpin) Breb. Alg. Falais. 66. 18.35. 



Colony of 2-8 cylindrical oblong cells, both ends obtusely rounded, the outer 

 cells of each series armed with a recurved spine; length of cells 12 u. 

 PL IV, Fig. 9. 



Section II. — Cells more or less acute at each end. 



Scenedesmns obliqnns (Turpin) Kuetz Syn. Diat. 609. 1831. 

 Achnanthes obliqua Turp. Aperc. Organ. 312. 

 Scenedesmus acutus Meyen Beob. ueber Algenfl. 775. 1829. 



Colony four- to eight-celled; cells fusiform, both ends acute, either in a single 



or double series; diameter of cells 6-7 //. 

 Stagnant water. PI. IV., Fig. 10. 



Scenedesmus diinorphus (Tubpin) Kuetz. Syn. Diat. 80. 1834. 

 Achnanthes dimorpha Turp. Diet. 1820. 

 S. obliquus dimorphus De T. Syl. Alg. I. 567. 1889. 



Ceils fusiform, acute, 4-8 in a single row; inner cells fusiform with ends 



drawn out, often quite long; outer cells lunate. 

 Stagnant water. PI. IV., Fig. 7. 



9. HYDRODICTYON Roth Tent. Fl. Germ. III., 501. 1800. 



Colony formed of oblong, cylindrical cells united at the ends into a reticulate 

 mass; cells very numerous, at first minute, finally 5-10 mm. long, cylin- 

 drical; propagation by macrogonidia which join themselves into a colony 

 within the mother-cell; reproduction by formation of numerous micro 

 gonidia furnished with two or four cilia, which escape from the mother- 

 cell, copulate, and form a resting spore which after a time germinates, 

 forming a saccate colony. 



Etymology: Greek vdup, water, and 6iktvov, net work. 



Hydrodictyon reticnlatum (L.) Lagerh. Bidrag till Sveriges Algf. 71. 1883. 

 Conferva reticulata L. Spec. PI. 1165. 1753. 



Colony varying almost indefinitely with age; cells 1-10 mm. long, 100-200 /i 



broad; macrogonidia 10x8 /*; microgonidia 3-6x5-8 /i. 

 Clear water. PI. IV., Fig. 6. 



