36 THE FLORA OF NEBRASKA. 



SYNOPSIS. 



Fam.— Desmidiaceae.— Cells symmetrical, single or rarely in a simple filament, 

 often constricted in the middle, resting spore giving rise to 1-8 plants. 



Fam— Diatomaceae.— Cells typically bilaterally symmetrical, single or united 

 into filaments, yellowish brown, cell-wall silicified, variously marked; 

 otherwise as in Desmidiaceae. 



Fam.— Zygnemaceae.— Cells cylindrical, united in a simple filament, resting spore 

 giving rise to a single plant. 



Fam.— Mucoraceae.— Saprophytes or parasites; asexual reproduction by internal 

 spore-formation in sporangia, or by conidia or conidia chains; sexual re- 

 production by zygospores. 



Fam— Eiitomoplithoraoeae.— Parasites on insects; asexual reproduction by 

 conidia produced singly on the ends of unbranched threads; sexual re- 

 production by zygospores. 



Faniily.-DESMIDIACEAE. 



Aquatic, rarely found on damp rocks or moss; cells solitary, or associated in filiform 

 (in one genus branched) filaments, cylindrical, fusiform, lunate, or cask shaped, often 

 constricted in the middle, variously crenate or laciniate; cell membrane thin, smooth or 

 verrucose, devoid of silica; propagation by cell division; reproduction by the union of 

 2 similar free cells which form a resting spore (zygospore); zygospore thick walled, 

 often involved in a gelatinous covering, epispore smooth, verrucose or aculeate. 



Sub-fam I.— Endesmidieae.— Cells united in filaments. 



Cells united along the whole of each end or only at the outer portions of 



each end Desmidium 



Cells united by a narrow isthmus Sphaerozosma 



1. 1>ESMI1>U!M Ag. Syst. 9: 1824. 



Filaments 3-4-angled or compressed, regularly twisted, joints bidentate or 

 bicrenate at the angles or lateral margins; cells either united along the 

 whole of their end margins or only at the outer portion of each by a 

 mutual projection; zygospore globose or oblong, smooth. 

 Etymology: Greek, a diminutive from dea/wg, a chain. 



IK'S in nl in in a ptogoni inn Breb. Alg Falaise 65. 1835. 



Filaments naked, perforate; cells quadrangular, 22-44 fi broad, about the 

 same in length, with two rounded crenations on each lateral margin, 

 united at the outer portion of each margin by mutual projections pro- 

 ducing oval foramina. 



Minden. PL VI., Figs. 7, 7 a. 



Desmidiinii swartzii Ag. Syst. Alg. 9. 1824. 



Filament triangular, with a single, longitudinal, wavy, dark line; cells in 

 front view quadrangular, broader than long, with two somewhat angular 

 crenations on each lateral margin; end view triangular with chlorophyll 

 three rayed; zygospores oval, 30x23-28 m cells of the filament 45 fi broad, 

 19 ii long. 

 Minden. PI. VI., Fig. 6, 6 a end view. 



