FRESH-WATER ALG^ OF THE UNITED STATES. 45 



W. lobatus, Wood. 



N. thallo vivide viride aut luteo-viride, cavo, enormiter lobato, natante, modice magno, firmo, 

 gelatinoso ; trichomatibus plerumque loagis, flexuosis, dilute viridibus, plerumque articulatis, 

 partim inarticulatis, cylindricis aut sub-moniliformibus, sparse granulatis. 



Z)wm.— Trichora. teW = .00006"— 7-5^/ = .00013" ; cell perdum. ^^^Z = -00026". 



Syn N. lobatus, Wood, Prodromus, Proc. Amer. Philos. See, 1869. 



Hab. — In. Schuylkill Flumine, prope Philadelphia. 



Thallus bright green or yellowish-green, hollow, irregularly lobed, floating, moderately large, 

 firm, gelatinous ; filaments mostly long, flexuous, dilute green, mostly articulate, partly inar- 

 ticulate, cylindrical or somewhat moniliform, sparsely granulate. 



Remarks. — I found this plant floating upon the Schuylkill River just above 

 Manayunk. The hollow frond was buoyed up by a bubble of gas contained within 

 it. It was an irregular, flattened, somewhat globose mass, of a bright green color 

 and about half an inch in diameter. It seems very probable that in its earlier 

 condition, it was a solid attached frond. The long slender filaments are often very 

 tortuous, but run a pretty direct general course towards the outer surface. 



Fig. 6 a, pi. 3, represents a section of the frond slightly magnified ; a, b, c, por- 

 tions of filaments magnified 800 diameters. 



Genus GLOIOTRICHIA, J. Ag. (1842.) 



Trichomata e planitie orta pseudoramosa, distincte vaginata ; vaginae amplse, basi plerumque 

 saccatse, transverse undulato-plicatse, plus minus constrictae, apice apertse, non laciniatse. Sporae 

 magnae cylindricse. 



Filaments springing from a plane, pseudoramose, distinctly vaginate ; sheath ample, mostly 

 saccate at the base, transversely undulately plicate, more or less constricted, open at the apex, 

 not laciniate. Spores large, cylindrical. 



Remarks. — This genus was, I believe, first indicated by Professor Agardh in 

 his Algoe Mao-is Mediterranei et Adriatici, a work to which I have not access. 

 On account of this, and also because I have not seen any of the typical species 

 of the genus, I have preferred simply copying the generic characters given 

 by Professor Rabenhorst. If my understanding of "e planitie orta" is cor- 

 rect, I do not think it true. Professor Rabenhorst's own figure of Rividaria 

 shows that the filaments do not all arise on one plane ; although he asserts the 

 character equally for that genus. In our American species the filaments do not 

 all arise on one plane, nor can they be spoken of as "■pseudoramosa." 



G, incrustata, Wood. 



G. globosa vel subovalis, firma, solida, ad pisi minimi magnitudinem, dilute viridis, crystallo- 

 phora; trichomatibus rectis aut leviter curvatis, in pilum productis, viridibus aut flavescen- 

 tibus, ssepe infra Isete viridibus sed supra flavescentibus, baud ordinatim articulatis ; articulis 

 inferioribus in trichomatibus maturis brevibus, plerumque compressis ; pilo apicale recto aut 

 leviter curvato, plerumque indistincte articulato, saepe interrupto ; vaginis amplis, achrois, 

 saccatis, interdura valde constrictis ; sporis cylindricis, ssepe curvatis, diametro ad 9 plo lon- 

 gioribus ; cellulis perdurantibus sphsericis. 



