FRESH-WATER ALG^ OF THE UNITED STATES. 43 



Diam— Artie. ^^\^" = .00016" ; spor. tbSu/— tsW = .00026"— .00033". 

 Syn. — S. Carmichselii, Harvey, Phycol. Brittanica, T. cxiii. 



S. polysperma, (Ktz.) Rabenhorst, Flora Europ. Algarum, Sect. II. p. 192. 

 Eab. — In stagnis, New Jersey. 



S. filaments mostly subsolitary, but sometimes associated and interwoven together, light bluish- 

 green, straightish, or variously curved and flexuous ; articles either subspherical or shortly 

 cylindrical ; heterocysts globose or very broadly elliptic, a little larger to twice as large in 

 diameter as the ordinary joints ; spores more or less elongate, cylindrical, in the uncertain 

 condition sparsely granulate, light bluish-green, with the membrane not distinct, in the 

 mature state densely granulate, and with a thickish membrane. 



Bemarhs. — I found this species growing in a brownish jelly, with various other 

 algae, in a. pool east of Camden, New Jersey. The filaments were mostly scattered, 

 but in some places numbers of them were collected in little masses. In some fila- 

 ments almost all the cells were developed into spores, so that a single thread con- 

 tained ten or even more spores. In by far the larger number of such cases there 

 was between each pair of spores a heterocyst ; sometimes, however, the latter was 

 wanting, and the spores would be attached to one another. 



My specimens diflfer somewhat from the European form, but are too close to 

 separate from them. They equally resemble, however, S. CarmicJiceUi. Indeed, I 

 cannot see any sufficient reason for separating the species. S. CarmicJiceUi is, to 

 be sure,, a salt-water plant. I have, however, received specimens collected by Dr. 

 Lewis, near Stonington, which I believe grew in salt water, and which agree in 

 every respect with my fresh-water specimens. 



Fig. 3, pi. 3, represents a portion^ of a filament, magnified 750 diameters. 



Family RlVULARIACBiE. 



Thallus gelatinosus, mollis vel induratus, vel crustaceus, interdum calce impletus, subglobosus 

 vel amorphus. Trichomata ad oscillarium morem articulata, vaginata, sed interdum aetate provecta 

 cum vaginis in gelatinam matricalem confluentibus et baud visibilibus, simplicia vel pseudoramosa, 

 superne attenuata, saepius in apicem piliformem longe producta, parallela vel radiatim disposita, 

 cellula basale hyalina globosa et interdum cellulis interstialibus instructa. Sporae (manubria, Ktz.), 

 singulae plerumque inter cellulara perdurantem basilarem et cellulas vegetativas positae, saepe per- 

 magnae, cylindricse, plerumque pachydermaticse. 



Vegetatio terminalis. Propogatio sporis tranquillis. 



Thallus gelatinous, soft, or indurated, or crustaceous, sometimes filled with lime, subglobose or 

 amorphous. Trichomata articulated like an oscillatoria, vaginate, but sometimes, when old, with 

 the sheaths confluent in the maternal jelly and not visible, simple or pseudoramose, attenuated 

 above, often with the apex prolonged into a long hair, parallel or radiately disposed, furnished with 

 globose hyaline, thick-walled basal cells, and sometimes with interstitial cells. Spores cylindrical, 

 generally placed between the basal and vegetative cells, often very large, mostly with thick coats. 



Vegetation tranquil. Propagation by means of tranquil spores. 



Bemarhs. — In the Bivulariacece the thallus is always small ; but is most gene- 

 rally in the various species somewhat definite in form and size. Its consistency in 

 our North American forms varies from that of an exceedingly soft, formless jelly 

 to that of a gristly mass. The maternal jelly is usually colorless, sometimes brown- 

 ish or yellowish. There is never any condensation of the outer portion of the 



