70 FRESH-WATER ALGJD OP THE UNITED STATES. 



articulatis ; vaginis firmis, aureo- vel rubido-fuscis, in ramulis saepe subluteis, haud distincte 

 lamellosis; cellulis perdurantibus plerurnque modice uunierosis, singulis, subglobosis, saspe 

 valde compressis, dilute fuscentibus. 



Diam. Plerumque T5 VW' TsVW' = .0003" .001" ; max. 30 4 / = .0013"; cell, perdurant. 



TW = - 00058 "- 



Syn.Scytonema compactum, AGARDH. Syst. p. 38, N. 3. HARVEY'S Manual, p. 154. 

 Hassalia compacta, HASSAL, Fresh-water Algae, p. 232, t. Ixviii. f. 3. 

 Sirosiphon compactus, (Ao.) KTZ. RABENHORST, Flora Algarum, Sect. II. p. 287. 



Hob. In rupibus ealcareis, New Jersey. (Austin.) Prope Salem, Mass. (Russel.) 



Stratum expanded, tomentose, fuscous-black; filaments and brandies ascending, with their 

 obtuse ends sometimes slightly attenuate but often clavate; internal filaments composed of a 

 single series of cells, mostly moniliform; cells shorter than or nearly as long as broad, 

 subglobose or subquadrate, often compressed; apical cell cylindrical and articulate somewhat 

 like an oscillatoria; cytioplasm light bluish-green, finely granulate; sheath firm, reddish or 

 yellowish-brown, yellowish in the branches and near the ends ; heterocysts mostly rather 

 numerous, single, subglobose, brownish. 



Remarks. The specimens from which the above description was drawn up 

 were received from Messrs. Austin and Russell, and have been considered as 

 identical with the European S. compactus, although not in absolute agreement 

 with the descriptions thereof. The most important of the differences are in the 

 matter of size, the measurements given by Prof. Rabenhorst not equalling those 

 attained to by the American plant. 



The differences, however, do not seem sufficient to separate the forms, and, 

 in the absence of European specimens, the two have been considered one species. 

 The sheaths in the older portions of the filaments are nearly opaque, but in the 

 branches and younger portions they are quite translucent. The heterocysts some- 

 times are truncate at one end. The internal cells are rarely arranged in a double 

 series, such arrangement is, however, much more common in the specimens re- 

 ceived from near Salem, than in those found in Northern New Jersey. Mr. Rus- 

 sell's specimens are labelled as growing on shaded and moist rocks in patches two 

 or three inches wide. 



Fig. 3 a, pi. 8, represents the end of a filament of this magnified 150 diameters; 

 3 6, a fragment magnified 250 diameters ; 3 c, a heterocyst magnified 860 dia- 

 meters. 



S. Crameri, BRUGG. 



S. csespitibus, tomentosis, spatiose expansis, fusco-nigris ; trichomatibus vage ramosis; ramis 

 plerumque singulis, saepe elongatis, saepe clavatis ; cellulis internis uniseriatis, diaraetro sub- 

 Dsqualibus vel brevioribus, interdum subglobosis, ssepe subquadratis, in aetate proTecta saepe 

 e pressione mutua valde compressis et transverse oblongis, aureo-fulvis vel in setate juvene 

 interdum aerugineis ; cellulis terminalibus in massam subeylindricam coalesccntibus ; cellulis 

 perdurantibus nullis; vaginis aureo-fuscis in aetate provecta plus minus subopacis et distincte 

 lamellosis, in aetate juvene plus minus pellucidis et saepe coloris expertibus. 



Diam Trich. cum vag. max plerumque .002"; interdum .00225"; ram. .0015" .0025" ; trich. 

 sine vag. .00083". 



Syn.S. Crameri, BRUGG. RABENHORST, Flora Europ. Algar., Sect. II. p. 288. 



