154 PEDIASTEUMS OF THE UNITED STATES. 



Sometimes the cells and the horns are distinctly granulate. 

 These constitute the variety granuUdum, Kg. 

 Frequent, Massachusetts to Florida. 



P. PERTUSiM, Kg. Plate LIII, tigs. 33, 34. 



Coenobium, more or less orbicular, pierced with many 

 lacunae; variable in size; composed of 163264 cells. All 

 the cells more or less loosely connected : attached at the angles 

 only, having an opening between the sides, and between the 

 connecting end of one, and the base <>t' the adjoining cells. 

 Cells of tin' periphery deeply bilobed ; lobes conical or horn- 

 like, sometimes acute, sometimes obtuse or truncate. 

 Frequent in pools everwhere. 



Var. BRACHYLOBUM, A. Br. Plate LIII, fig. 35. 



Differs from the typical form in having the cells of the 

 periphery emarginate, notched, or shortly two lobed, or lobes 

 almosl obsolete ; cells of the disc perforated with smaller 

 openings. 



Var. ci, Aim;. \ 1 1 \i. A. Br. Discs pierced with larger opening-; 

 the lacuna' being often a- large a- the cells. 



P. Ehrenbergii, (W-la.i A. Br. Plate LIII. figs. 25-27. 



Marginal cells closely united, bilobed, inedianly deeply 



incised; each lobule with ends truncate and notched or incised. 

 Coenobium not perforated, composed of 4816 32 cells. 



Var. CUSPIDATUM, A. Br. Plate LIII, fig. 25. 



A small form, with lobes of cell- finely, and often indis- 

 tinctly bidentate. 



Nut so frequent as the preceding forms, but widely dis- 

 tributed. 



P. tetkas, Ehrb. Plate LIII, fig. 24. 



Coenobium very small, four-celled, separated by colorless 

 interstices which form a cross. 



A. Braun. has a variety of P. Ehrenbergii, var. truncatum, 

 very near this form, but differs in having the ends of the lobes 

 notched our form, as far as observed, is perfectly square, 

 hence I retain the old name. 



Occurs frequently from Rhode Island to Florida. 



