58 FRESH- WATER ALGJS OF THE UNITED STATES. 



brandies whatever, and I have never seen more than a single pair, or, at most, 

 three branches to a filament. The mass of filaments is blackish-green, somewhat 

 tomcntose and quite shiny in appearance. The articles are often very long, and 

 the internal filament is frequently in such cases enlarged into a sort of globular 

 node at the joint. Not at all rarely there is a very decided break in the endo- 

 chrome at the joints. 



This species is very close to S. Austinii, from which, however, I think it suffi- 

 ciently distinct. The points of difference are in the much firmer, much more 

 colored and opaque, and rougher sheath of that species; in the swollen ends of 

 the internal filament of S. Austinii, and its shorter articles, Avith the absence of 

 nodes or distinct interruption of the endochrome at the joints. The heterocysts 

 are also quite different in the two forms, whilst the filaments of /S. simplice are 

 much the longer. 



S. Aiislinii, WOOD, (sp. nov.) 



S. rupicola, strato tomentoso, caespitoso, crasso, fusco-nigro ; trichomatibus adscendentibus, 

 curvatis, plerumque simplicibus; trichomatibus internis serugineis vel fuscescentibus, articu- 

 latis vel inarticulatis, fine ssepe valde incrassatis ; articulis diametro plerumque multo bre- 

 vioribus, interdura longioribus ; vaginis rubido- vel aureo-fuscescentibus, sscpe sub-opacis, 

 firmis, indistincte lamellosis, in apice plerumque achrois et coloris fere expertibus, snperficie 

 subrugosa et hirta; cellulis pedrurantibus breviter cylindricis, vel subquadratis vel subglo- 

 bosis, interdum valde compressis et diametro multo brevioribus. 



Diam. Fil. cum. vag. .0006" .0008''; sine vag. .00016" .0004". 

 Hob. ID rupibus, "Little Falls, New Jersey." (Austin.) 



S. growing on rocks, stratum tomentose, and somewhat turfy, brownish-black ; tricliomata 

 ascending, mostly simple, curved ; internal filament seruginous or fuscous, articulate or inar- 

 ticulate, often very much thickened at the ends; articles much shorter to longer than their 

 diameter ; sheaths reddish or yellowish-fuscous, at the apex colorless and transparent, firm, 

 indistinctly lamellate ; surface rough ; heterocysts shortly cylindrical, subquadrate or sub- 

 globose, sometimes strongly compressed and much shorter than broad. 



Remarks. This plant occurs as a blackish stratum of one or two lines in thick- 

 ness, forming a sort of miniature turfy cushion upon the rock. When examined 

 with the hand-glass, this layer is seen to be composed of a great number of ascend- 

 ing curved filaments whose color, in some specimens, is a reddish-brown ; in 

 others, apparently younger, yellowish-brown. Under the compound microscope 

 the sheaths in the older filaments are seen to be much roughened externally and 

 irregular in outline. The young sheaths are smooth. The filaments are mostly 

 simple, since I have not seen more than a half dozen having even a single branch. 



The heterocysts are scattered at irregular intervals, and are remarkably irregular 

 in form sometimes much shorter than broad, sometimes several times as long. 

 As the ends of the filaments are approached the internal filament suddenly swells 

 out and increases sometimes to twice the diameter it has in the central part of the 

 filament. In the filament proper it rarely attains a diameter of more than .0003", 

 and is commonly about .00025", whereas at the ends it very generally approaches 

 the maximum .00042". 



