76 FRESH -WATER ALG^E OF T1IE UNITED STATES. 



Filaments closely interwoven into a deep olive-black turfy mass, very thick, irregularly and fre- 

 quently branched, yellowish-fuscous, variously curved ; branches polymorphous, their apices 

 mostly obtusely rounded ; series of cell in filament multifold, in branches 1-4 fold ; cytio- 

 plasm granulate, mostly deep brown, sometimes bright green ; sheaths thick, light yellowish- 

 brown, sometimes transparent. 



Remarks. The fronds are very irregular in form and size, much branched, and 

 so closely interwoven that they mostly cannot be separated without breaking. 

 The branches are sometimes short and stumpy, sometimes they are very long. 

 The color of the cells approaches somewhat to a chocolate, at times with a little 

 red in it so as to give something of a mahogany tint. The walls of the cells are 

 mostly very thick, but they are often lost in the general mass of the frond. In the 

 branches, the cells are often so closely crowded as to almost obliterate their walls. 

 In a few specimens I have found the cells to be of a bright green color, instead 

 of that just mentioned. The exact meaning of this I do not know ; it would 

 scarcely seem to indicate immaturity, for I have found it in the oldest portion of 

 large fronds, whose other parts were of the normal color. 



Fig. 1, pi. 10 represents a filament of this variety magnified 160 diameters. 



I have received from Prof. Ravenel certain dried alga?, labelled Stigonema 

 Ravenelli, BERKELEY, which appear to me to belong to this genus. In what place 

 Berkeley described them, if ever, I do not know, nor why he placed them in the 

 genus Stigonema. The following is a description of the species : 



S. strato sub-nigro; trichomatibus arete intertextis, ramossissimis, enormibus, varie curvatis' 

 ramulis brevibus et sublongis, varie curvatis, latis, apiee nonuihil attenuatis et obtusis ; tri- 

 chomatum et ramulorum cellulis arctis, enormibus, in serie duo-multiplici enormiter dispositis; 

 cytio-plasmate bomogeneo, laete viride ; vaginis aureis, lucidis. 



Diam. Max. trich. cum vag. 7 ^ a ". 



When dried blackish ; filaments closely interwoven, very-much branched, irregular, and variously 

 curved ; branches short or largish, variously curved, broad, their apices somewhat attenuated 

 and obtuse ; cells of the filament and its branches very close, irregular, Irregularly arranged 

 in a twofold or multiple series ; endochrome homogeneous, bright green ; sheath yellow, 

 semitranslucent. 



Remarks. This plant was collected by Prof. Ravenel on the now famous Look- 

 out Mountain. It is of a thick, bushy habit, and appears to form turf-like mats 

 of a line or two in thickness and of a blackish color. The filaments throw off in 

 all directions very numerous branches, some of which are short and stumpy, others 

 quite long, and are themselves the parents of numerous secondary branches. The 

 longer branches often rival the main filament in size, and like it vary continually, 

 in being irregularly expanded and contracted. There is never a long, articulated 

 cell, not even in the apices of the branches. The apices are often somewhat 

 attenuated, and are always more or less obtuse. The cells are -of a bright green 

 color, are very irregular in form, and are often very irregularly arranged in rows 

 of from two to five, both on the main filament and branches. The base of the 

 filament often gives origin to several small, cylindrical, root-like processes. 



