STATJRASTRTJM. 110 



wardlv. End Lobe wider than the others; all the lobes some- 

 what cuneate ; apex of end lobe concave ; the others sub- 

 rectangularly notched ; the angles of all the lobes truncate and 

 furnished, each with two short, sharp teeth. Cytioderm 



smooth. 



Diameter H2 //. 



Collected in a pond in the vicinity of Minneapolis, Minn. 



Genus, STAURASTRUM, Meyen. 



Cells in front view similar to Cbsmaritvin, end view, three to six 

 or more, angular ; angles obtuse, acute, or drawn out into elongated 

 horn-like processes. Chlorophyl more or less concentrated into a 

 central mass, margins radiating toward- the margins of the semicells. 

 Zygospores provided with -pine-. 



This genus contains a large number of species ; a- all are figured, 

 a complete analysis doe- not appear important, but for a general 

 guide they may be divided into four larger sections, in the order 

 observed in the following li-t : 



Section 1. Membrane of oella smooth, or rarely punctate or indistinctly 

 granular. 



-n riON II. Membrane verrucose, or rough with pearly granules. 



8b nou III. Membrane hairy, spinulose or aculiated. 



Section [V. Membrane with angles extended into arm, or horn-like processes. 



SECTION 1. 



St. mtjtictjm, Breb. Plate XXXIX. rigs. 11, 15. 



( .11- in front view orbicular, smooth, deeply constricted, 

 often involved in a mucous envelope; semicells elliptic ; end 

 view triangular, or rarely quadrangular; angles rounded, sides 

 slightly concave. 



Diameter 33-38 ,". Frequent. 



Var. Mi\C>Jl (Figs. 14, 15) does not differ from the typical form 

 except in size; measure only about one-half. 



Var. ELLIPTICUM. Fig. 13. This form i> more elliptic in front 

 view than the other-. 



Both of these varieties occur, but not as frequently as the 

 true form. 



