FRESH- WATER ALG.E OF TOE UNITED STATES. 37 



rate fronds are not distinct. Tin- filaments arc very long, mostly closely intricate, 

 very much cuned; in some places they are more sparse. Their color is mostl\ ;i 

 Miit of yellowish tcrru^inous-^rcen, sometimes they are, decidedly, almost purely 

 ferruginous, mure rarely a bright green. This plant agrees pretty well with the 

 description* of the Kuropean jY<W*- rt,miniitittn>n, und I Ix-lieve is the same 

 iesj if. howeNer, .V. laruntre of Kiit/ing i.s distinct from N. cominiiniliiiii, this 

 is also; lint 1 incline to the opinion that they are all different forms of one plant. 

 Fig. 3, pi. '.', represents a single filament magnified 800 diameters. 



IV. commune, v.\ 



rn stn , t hallo irrrgularitcr expanse, difformi, undulato-plicato, trcmulo, iotas aqaose gela- 

 .i. ;cta!<' provecta pliT<iim|uu exeavato, peridurmate gubuoriaceo finno, olivaceo, luti-o- 

 vcl luteo-fuseo cincto ; trichouiatibus fiexuoso-curvatis, pallidc erugineis, laxe 

 implicatis, ajqualibus vel saba-qualibus, baud raro a bawl ad medium usque ceilulis bmeriatis 

 ronipositis; nrtiriilis gphuricis vel e mutua prcssione snbquadrangularibns, laxe conncxis, 

 passim distantibua, puncto central! turbato prtcditis; ceilulis perdurantibus globosis, articn- 

 lorum diamctro duplo majoribus, interstialibus terminalibusque. 



Diam. Cell. vegetat .00012" .00016" ; cell, perdurant .00025" .00033". 



S;in. y. commune, VAUCH. RABENHORST, Flora Europ. Algarum, Sect. II. p. 175. 



Hub. In terrestre, New Jersey. (Austin.) " Rio BraTO. Schott" Harvey. 



Ti-rrrstrial ; thullus irregularly expanded, shapeless, undulate-plicate, tremulous, within of the 

 consistence of thin jelly, in advanced age mostly hollow; periderm subcoriaceons, firm, oliva- 

 ceous, yellowish-fuscous ; filaments flexuously carved, pale green, laxly implicate, equal or 

 siibequal, not rarely composed of a double series of cells from their base to their middle ; 

 articles spherical or subquadrangular from mutual pressure, loosely connected, here and there 

 distant, furnished with a central spot ; heterocysU globose, twice as large as the vegetative 

 articles, interstitial and terminal. 



U>-innrk*. The only specimens I have seen of this species are very old ones, 

 which have burst and discharged their central portions. I have consequently pre- 

 ferred to copy the diagnosis of Prof. Rabenhorst. My specimens agree pretty 

 closely with it. The filaments, and also the single cells, are closer together than 

 his words would seem to indicate. My measurements of the heterocysts, as given 

 above, are larger than those of Prof. Rabenhorst. They agree, however, with his 

 text, which his own measurements do not. I am indebted to Prof. Austin for 

 specimens of this species, which he collected in Northern New Jersey. According 

 to Professor Harvey this plant was collected by Dr. Schott along the Rio Bravo, 

 where it is common on dry flats after rains. 



SUBFAMILY SPERMOSIRKE. 



Thallas sine peridcrmate, interdum nullus. Tricbomata sporis instructa. 



Thallus without any periderm, sometimes absent. Filaments furnished with spores. 



Genus ANAB^ENA, BORY. 



Trichomata moniliformia, evaginata; uporis spbsericiB, anreis vel aureo-foscis, plcrumque lingalis, 

 cum eellulis vegctativis vel perdnrantibns conjunctis. 



