FRESH-WATER ALG^ OF THE UNITED STATES. 53 



well shown in figure 2 h, pi. 5. Associated with them were a number of similar cells 

 which had not obtained as yet the outer thick wall. The color of the filaments is 

 in my specimens of a rich golden brown j but, as they have been preserved in car- 

 bolic acid water, I cannot speak positively as to the original tint. The heterocysts 

 are subglobose, sometimes compressed, sometimes somewhat triangular. They 

 about equal in diameter the internal filament. 



Fig. 2, pi. 5, represents a small cluster of youngish filaments of this species. 



M. sejunctum, Wood, (sp. noT.) 



M. thallo csespitulo, molle, parasitico ; trichomatibns simplicibus, plerumque inarticulatis, sed, 

 interdum breve, interdum longe, articulatis, continuis, rarius interruptis, apice attennatis, 

 flavo-olivaceis aut viridibus, sparse granulatls ; vaginis plerumque amplis et distinctis, hya- 

 linis, saepius valde undulatis, apice plerumque valde amplificatis et in fibrillas solutis ; cellulis 

 perdurantibus diametro subsequalibus ; sporis nuUis. 



Diam.— Trichom ^^Vtr" = -00016"; cum vag. ^^Vtt" = -0005". 



Hob. — In plantarum aquaticarum foliis. Carp River, Michigan. 



Thallas somewhat csespitose, soft, parasitic ; filaments simple, mostly inarticulate, but some- 

 times shortly sometimes long articulate, continuous or more rarely interrupted, attenuate at 

 the apex, yellowish-olive or greenish, sparsely granulate; sheaths mostly ample and distinct 

 hyaline, often strongly undulate, the apex mostly much amplified and dissolved into fibrilloe ; 

 heterocysts about equal to the filament in diameter; spores wanting. 



RemarJcs. — This species was found in the Carp River bog, growing on the edges 

 of minute leaves, so as to form little prominences or thickenings of the margin. 

 The trichomata are quite distinct from one another, and can scarcely be said to be 

 united into a frond, although they all appear to radiate from the base, where they 

 are consolidated into a dense mass. The sheaths are generally quite distinct, much 

 broader than the cytioplasm, and are not sensibly dilated below. In most speci- 

 mens they are very distinctly alternately dilated and contracted, or in other words, 

 undulated. This is especially the case when the sheaths are quite wide. Above, 

 they are rapidly and widely dilated, are distinctly fibrillose, and appear to gradu- 

 ally melt away. The cytioplasm is rarely articulated, and, when it is so, the joints 

 are scarcely longer than broad, and are most generally confined to the distal end of 

 the filament. The species appears to be most nearly allied to M. Bauerianum, 

 Grun., from which, however, it is quite distinct. 



Fig. 2 a, pi. 4, represents this species magnified 250 diameters ; fig. 2 6, a single 

 filament magnified 800 diameters. 



M. elong^atum, Wood. 



M. initio subglobosum, postea ssepe nonnihil fusinum, nigro-viride, lubricum, firme ; trichoma- 

 tibus serugineis, valde elongatis, flagelliformibus, interdum inarticulatis sed ssepius breve 

 articulatis, interdum ad genicula valde constrictis, apice interdum truncatis sed plerumque 

 in pilum, longum, achroum, flexuosura, productis; vaginis achrois, arctis, saepe apice trun- 

 catis ; cellulis perdurantibus globosis vel subglobosis. 



2)iam—TgV' = . 00026." 



Syn. M. elongatum, Wood, Prodroraus, Proc. Araer. Philos. Soc, 1869, p. 128. 



Eab. — In aquario. 



