26 DESMIDS OF THE FNITED STATES. 



Specimens occur frequently in pools and ponds all over the 

 country, rarely unmingled with other forms. It is readily 

 distinguished hy its large size, deep incisions of the border, 

 and twisted outline. 



I), quadratum, Nbrd. Plate XLIX. fig. 5. 



Differs from the preceding in the cells being nearly as long 

 a- broad, and viewed from the side, quadrate. The breadth 

 of tlif cells is onlv about one-fifth more than the length ; tin 1 

 thickness, the same a- the length. < 'hlorophyl mas- in cadi 

 cell in end view, more or less radiate. 



Diameter 15 .; length, 3338 ".: thickness, 3338 u. 



Found this form repeatedly during the past four years, but 

 rarely, except in ponds, Brown's Mills, New Jersey. Ii varies 

 in >i/.e from the Norway typical plant, in being considerably 

 larger; otherwise it appeal- to be identical. 



I>. long \ mm. Wolle. Plate X LI X. fig. 6. 



Filaments thin ; cells in front view nearly twice a." long :i- 

 wide; in side vie^ nearly 1\ time-, longer than broad; closely 

 united without a thickened border at their junction ; end view 

 broadly elliptic. 



Diameter, widest part, 28//.; thickness, hi 18 ".: length of 

 -ell, 35-40 ". 



This interesting new species from Brown's Mills, New 

 Jersey, was found late in the season September 22, 1883); 

 no gelatinous sheath was observable ; the filaments were 



hyaline except two chlorophyl nuclei in each cell. 



I . M\ artzii, A.g. Plati I I. figs. 1 6. 



Filament triangular, with a single longitudinal, waved, dark 

 line formed by the third angle, (compare fig**. <. 8, 13 : joint- 

 in front view somewhat quadrangular, broader than long, with 



two slightly angular crenatures -adi lateral margin, united 



at the whole of their end margins l>\ a thickened border; end 

 view triangular with tin chlorophyl three-rayed. Zygospores 

 oval. 



I hameter .''.<; ".. re or leas. 



Frequent in shallow pools, trenches ami the like. 

 The spores mi-.' tunned by the flowing together "t the two 

 rnasses of chlorophyl in epch pell ; the united bod) assume* 



