22 DESMIDS OF THE tNTTF.D STATES. 



Genus, GOXATOZYGON, D. By. 



Cells long, cylindrical, or Truncate spindle form, without con- 

 striction, united into fragile, filiform straight series; at maturity 

 they separate and become geniculate, copulate and produce spheri- 

 cal zygospores; these separate quickly from the empty cells. 



Two Bpeciea only have been recognized in this country. 



( i. asperum, i Ralfs) Rab. Plate 1. tig. 1 . 



('ells long, cylindrical, ten to twenty time- a- long a- wide, 

 very Blightly, or not at all reduced in thickness at the ends. 

 < lytioderm fine-granularly roughened. 

 Diameter 11-12 >>. 



Occurs frequently in | > > i < 1 - of New Jersey. 



<J. imi.us.vm. Wolle. Plate 1. fig. 2. 



( Jells twelve t' twenty times a- long as wide, loosely con- 

 nected; cytioderm more ir less densely clothed with small, 

 straight hairlike spines; cells cylindrical, terminal one of a 

 filament slightly attenuated, end rounded. 



. , 



I Hameter 1 5 .: w ith spines 25 ". 

 Habitat the -aim- as the preceding 



Genw, HYALOTHECA, Ehrb. 



Plate I. figs. 3-1 t. 



Cells short, cylindrical, usually with a slighl obtuse constriction 

 in the middle; disciform in end view, closely united into long fila- 

 ment-, which are inclosed, each in an ample, colorless mucous 



-heath. < 'hlorophyl ma in each cell, end view . -i\ to ten radiate. 

 (/) 1. ius,u,/.ii-:\~. Sn lire!,. Mate I. f gs. 3, I. 5 



1 1. DigJLiJENs, (Smith Br 

 Filaments elongated 



d. cells slightly contracted in the middle, 

 usually about half as long as broad. Variable in size. 

 Diameter 20 36 u. 



Frequent in ponds and Bluggish, shallow water-. I he fre- 

 quency of this plant .-(inn familiarizes it ; usually it is 

 found intermingled with other forms, but sometimes it has 

 entire control of Bmall pools, trenches and outlet- of springs. 

 In its younger Btate it is attached to the muddy bottom, or 

 sticks or stones ; bul inure commonly, it is tumid in floating 

 masses, The filaments are generally fragile, l>m sometimes the\ 



