168 F RE S II- W ATE 11 ALG^ OP TUE UNITED STATES. 



clobosis aut ovalibns, ant subcylindncis, dianietro fequalibus aut | plo longioriljus ; artictilis 



fcrtilibns cylimlricis, hand tumidis. 



Diam.— Art steril. ^lU' = -00-2 ; spor ^l'/ — .002". 



Sy„. Sp. duhia, KuTziNG. Rabenhorst, Flora Eiirop. Algarum, Sect. III. p. 243. 



//„/,. — lu stag-nis, propc Philadelphia. 



Green, in fruit light green; sterile joints cylindrical, l|-2l times longer than broad; spiral 

 filaments 2-3, very narrow, nodose, la.x, turns 1-2 ; cytiodcrm neither infolded nor protruded 

 at the end, rather thick ; zygospores polymorphous, either subglobose, oval, or subcylindrical, 

 as broad as long to J times longer; fertile articles cylindrical, not enlarged. 



Remarks. — I have fotmd this species growing in the ditches below the city, fruit- 

 ing iibundantly in INIay. When in tliis condition it forms masses of a dirty, hghtish, 

 yellowish-grccn. Tlic spores mostly fill pretty well the fertile cells. My specimens 

 do not agree completely with the descriptions given of the European. The two 

 forms, however, completely overlap one another, except in one character, namely, 

 the shape of the sporangial cell. I liave never seen it swollen or at all tumid in 

 American specimens, whilst in the European it is said to be " modice tumidis." 

 This difference alone does not, however, seem to me sufficient to characterize a 

 new species. I have seen specimens of this plant collected by Dr. Lewis at Cobble 

 Mountain. They agree well with the Philadelphia specimens, except in attaining 

 a little larger size, .0021", and in the sterile filaments having their walls very thick. 

 The character of non-inflation of sporangial cells is perfectly preserved. 



Fig. 4, pi. 17, represents this species. 



Sp. rirularis, (Hass.\ll) Rabenk. {non Ktz.) 



Sp. saturate viridis, Inbrica; articulis sterilibiis diametro "I-ll plo longioribus; fertilibuscylin- 

 dricis aut vix tumidis; cytiodermato tenuissimo, utroquc line nee protenso nee replicato, 

 fasciis 4, lase spiralibus, modice angustis, nodulosis et seiTatis, aufractibus 2| ; zygosporis 

 ellipticis, diametro 2-2^ longioribus. 



Diam.— Art ster. ^/^/-^IJ/ = .0012"— .OOUG" ; spor. ^ig^—^lg/. 



Syn. — Zygnema rivularis, IIassall, Fresh-Water Algte, vol. i. p. 144. 



Spirogyra rivularis, (Hassall) Qion KiJTZiNG) Rabenhorst, Flora Europ. Algarum, 

 Sect. III. p. 243. 



Ilab. — In rivulis, Florida ; (Canby) Wood. 



Deep green, slippery ; sterile articles 7-11 times longer than broad, fertile cylindrical or slightly 

 tumid ; cytioderm very thin, neither infolded nor protruded at the end ; chlorophyl filaments 

 4, laxly spiral, moderately narrow, nodose and serrulate, turns 2^ ; zygospores elliptical, 

 2-2^ times longer than broad. 



RemarJcs. — This species was collected by Mr. Wm. Canby in Pine Barren Run, 

 near Hibernia, Florida. It is rather smaller than the European forms, but does 

 not appear to be distinct from them. Rabenhorst, indeed, states that there are 

 only two or three chlorophyl spiral bands in a cell, but Hassall in the description 

 of the type states distinctly that in some instances there are four bands, and alsc 

 figures the plant so. 



Fig. 5 a and h, pi. 17, represents sterile cells of this species, magnified 26C 



