58 FRESII-WATEK A L G .E OF THE U .N 1 T E D STATES. 



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

 tliree branches to a fihimcnt. The mass of fihinicnts is blackisli-grecn, somewhat 

 tomentose and quite shiny in appearance. Tlie articles are often very long, and 

 tlie internal filament is frequently in suck 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. Anstinli, from which, however, I think it suffi- 

 ci(Mitly distinct. The points of difference are in the much firmer, much more 

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

 the internal filament of ^S'. Avstinii, and its shorter articles, with the absence of 

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

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

 nuich the longer. 



S. Aii!«li»ii, Wuup, (sp. iiov.) 



S. nipic'ola, strato tomentoso, csespitoso, crasso, fiisco-nigro ; trichomatibus adscendcntibus, 

 curvatis, plcniniqiic siiiiplicibus ; trichomatibus intcniis itrugineis vel fuscescentibus, articu- 

 latis Tcl iiiarticiilatis, fine sa>pe valde incrassatis ; articulis diametro plerumque multo bre- 

 Tioribus, interdiiiu longioribus ; vaginis riibido- vel aureo-fuscescentibus, s»po sub-opacis, 

 firmis, iiidistiiicte bimellosis, in apice plerumque achrois et coloris fere expertiljus, snperficie 

 subnigosa et birta; eellulis pedrurantibus breviter cylindricis, vel subquadratis vel subglo- 

 bosis, iiiterdum valde couipressis et diametro multo brevioribus. 



Biam.—FW. cum. vag. .OOOG"— .0008" ; sine vag. .00016"— .0004". 

 Ilah. — lu rupibus, "Little Falls, Jsew Jersey." (Austin.) 



S. growing on roek.s, stratum tomentose, and somewhat turfy, brownish-black ; trichomata 

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

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

 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. 



Be I narks. — 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 Avhose 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 brancli. 



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 .0004:2". 



