364 ALG/E CONFERVOIDEiE. [St y lone ma. 



authentic specimen of which I have compared our plant. The only 

 difference I can perceive lies in the generic character, and this I am al- 

 most inclined to suspect, depends on age ; for I find the apices of the 

 branches simply striated, like a Calothrix or Scytonema, and the smaller 

 branches, for at least part of their length, have thesemipunctate appear- 

 ance of Scyt. ocellatum; and it is only in the' larger and main branches 

 that the punctated character is clearly visible. Should my ideas prove 

 correct, the Stigonemata must only be regarded as Scytonemata, arrived 

 at full perfection. 



72. Scytonema. Ag. Scytonema. 



Filaments branched (very rarely simple), flaccid, tough, con- 

 tinuous, tubular. Endochrome brown or olivaceous, transverse- 

 ly striated, " at length separating at the striae into lenticular 

 sporidia." Carm. — Name; gxvroc, a skin, and vrn^a, a thread; 

 in allusion to the toughness of the filaments. — Agardh strangely 

 places this genus between Trentepohlia and Protonema, with 

 neither of which has it the least affinity. Captain Carmichael, 

 whom I gladlyl follow in removing it to the Oscillatoriece, 

 remarks, with his usual acuteness, the strong affinity that sub- 

 sists between it and Lyngbya, " the internal structure of the 

 filaments being nearly, if not absolutely, the same in both : 

 that is, the filaments in botii are continuous tubes, filled with a 

 transversely striated granular mass, which at length separates 

 at the striae into lenticular sporidia." Carm. MSS. — Scyto- 

 nema is still more closely related to Calothrix, from which I 

 find it very difficult to distinguish it by a satisfactory char- 

 acter. 



1. S. ocellatum, Harv. (beaded Scytonema); filaments long 

 gelatinous pale-brown flexuose, branches solitary slightly con- 

 stricted at the base obtuse divaricating. — Conferva ocellata,Dillw. 



Syn. Conf.p. 60. t. D E. Bot. t. 2530. (not S. ocellatum, Lyngb. 



Hydroph.Dan. t. 28.) — S. myochrous, (3. ocellatum, Ag. Syst. Alg. 

 p. 40, (according to the references to Dillw. and E. Bot.) 



Alpine bogs. — Filaments tufted, erect or decumbent, gelatinous, pale 

 yellow- brown, twice or thrice as thick as those of S. myochrous, 

 branched; branches irregularly disposed, issuing from the centre of 

 the filament, somewhat attenuated at their base, very obtuse and 

 slightly thickened at the extremity, erecto-patent, solitary or extremely 

 rarely in pairs, the larger ones with a few short ramuli. Sporidia distant, 

 broad, at first quadrate, but becoming sphaerical and finally longitudi- 

 nally divided into two portions; .margin of the filament very broad. — 

 Agardh is surely not acquainted with the true Conf. ocellata of British 

 authors, or he would scarcely have confounded it with S. myochmus, 

 from which it differs in every, save the generic, character. Dillwyn 

 well remarks, that it is most nearly allied to Stigonema atro-virens, and 

 it seems indeed to be intermediate between Scytonema and Stigonema; 

 the division of the sporidia, in old filaments, assimilating it to the latter 

 genus. Lyngbye's figure and description belong to S. myochrous. 



2. S. compdctum, Ag. (compact Scytonema); " filaments de- 



