THE FLORA OF NEBRA8B \. 



«. PEDIASTBUM Meyen Beob. ueber Algenfl. 72. L829. 



Colony plane, disc-shaped or Btar-shaped, freely Bwimming, formed ol cells 

 in a single or in part double stratum which is continuous or perforated; 



cells polygonal, 4 Gl or even more, com. >nts green, homogei i-. then 



granular; propagation by cell contents dividing into macro gonidia which 

 break through the membrane, and, altera stunt period ol motile life, come 

 to rest, divide, and form the mature plant. 

 Etymology: Greek rredtov, plane, and aorpov, Btar. 



Pediastrum tetras (Ehrb.) Ralfs Ann. & Mag. X. u xi v.. 169. 

 Micrasterias tettas Ehrb. Inf. 155. is ; ;. 



Colony very small, four-celled (rarely more), separate I by colorless interstices 



which form a cross; marginal cells 8-24 „ wide. 

 Standing water, Lincoln. PI. IV., Fig. 17. 



Pediastrum aiignlosum (Ehrb.) Menegh. Synops. Desm. 210. 1840. 

 Micrasterias angulosa Ehrb. Inf. 158. 1836. 



Colony orbicular, oblong, or subreniform, composed of 8 64 cells, as large as 

 120 fj. in diam.; cells all smooth, angular, 19 ft broad, marginal cells with 

 angular lobes not extended into rays. 

 In ponds, Thedford. PI. IV., Fig. 20. 



Pediastrum boryanum (Tubpin) Menegh. Synops. in Linn. 210. 1840. 

 Hierella boryana Turpin. Mem. Mus. Hist. Nat. XVI., 319. 1828. 



Colony orbicular, oblong, or elliptical, bright green, variable in size. c.im].o-...l 

 of 8-128 cells, marginal cells twolobed, each drawn out into aoolorless 

 horn-like process, short or long, rather obtuse, sometimes a little tliiek 

 ened at the end; cells 4-6-augled, membrane punctate. 

 In ponds etc., Thedford. PI. IV., Fig. 18. 



Pediastrum duplex Meyen Beob. ueber Algenfl. 72. 18:29. 

 P. pertusum Kuetz. Phyc. Germ. 143. 1815. 



Colony more or less orbicular, pierced with many lacunae, variable in size, of 

 16-64 cells, attached at the angles only, having an opening between the 

 sides and between the connecting end of one an. I the base of the adjoin 

 ing cell; marginal cells deeply two lobed; lobes conical, acute or obtuse. 



Var.— clatliratnm A. Br. — Marginal cells 10-24// broad; lacunae as hire as the 



cells. 

 Ponds etc., Minden. PI. IV., Fig. 19. 



7. SORASTRIJI Kuetz. Phyc. Germ. 144. 1845. 



Colony globose or subglobose, solid within, of 1 32 compressed wedge ah i 

 cells, which are sinuate emargiuato or MlM at the apes and radiately 

 disposed; propagation by separation of the cells of the colony, eaoh oeU 

 dividing into 2, each of which forms a new colony. 



Etymology: Greek trupoc, heap, and aarp . Btar. 



Sorastrnm spiunlosum Naeo. Gatt. Kin/ell. Alg. 99. 



Colony globose, 25-75 // in diam.; cells 8 32, I riangular, ouneate, apex allghtly 

 emarginate. obtusely rounded, with two spines, 15 long, about equal in 



diameter. 

 Standing water, Minden. PI. IV., Fig. 16 a, b. 



