PESTOM. 35 



Prevails over a wide range. I have it from Vermont, 

 Connecticut, and almost every State southward to Florida, 

 also from the wrest to Minnesota. 



It varies somewhat in size, but is easily recognized bv the 

 arrangement of the granuli 



P. lnterruptum, Breb. Plate V, figs. 1 1. 15. 



Broad cylindrical, not constricted, 5 6 times as long as wide, 

 suddenly tapering, cuneate mar the end-, apices rounded. 

 Chlorophyl deep green, in matured |>lant~ interrupted by three 

 transverse pale bands; cytioderra smooth. 



Diameter 38 I I u. t rarely only 16-20 u. 



rlabital the same as the preceding, rather more frequent ; 

 adily distinguished by its transverse bands and cuneate 

 ends. 



P. CLO8TERIOIDE8, Ralfs. Plate V, fig. 18. 



( Jells narrow ly lanceolate, 56 times longer than the greatest 

 diameter; sensibly attenuated from the middle to the rounded 

 apices. Chlorophyl contents interrupted in the centre. 

 Diameter !<-} I -. 



Pond.-. New Jersey and Pennsylvania. 



In its general appearance and in the arrangement of the 



chlorophyl, tin- plant has a strong resemblance to a Clos- 

 terium, but van.'- in being always straight and having the 

 opposite margins symmetrical. 



P. truncatum, Knit"-. Plate V, figs. 9, 10, 21, 22. 



Cylindrical, not constricted, 3-4 times longer than wide, 

 end- truncate, square. Zygospores smooth, spherical. 



Diameter 1 1-12 //. 



Ponds, northern comities of New Jersey. The chlorophyl 

 is usually more or less interrupted in the middle, producing 

 a pale transverse band; membrane smooth or finely punctate. 



P. minutum, Cleve. Plate Y, tig-. 19, 20. 



Slender, cells 4-6 times longer than broad, sides straight, 

 end- rounded, without inflation, and without punctures. 

 Diameter 1 115 u. 



This small form, perhaps more properly a Calocylindrus, 

 (Plate XII, fig. 12), has not come under my notice. It is 



