20 FRESH-WATER ALG^ OF THE UNITED STATES. 



When grown in a bottle, the plant appears as a very thin stratum growing up the 

 sides. The agreement of this plant with the descriptions of the European 0. limosa 

 is very close, so that I do not think it can be separated from it, although in 0. 

 limosa the dissepiments are said to be distinctly granular. 



Fig. 4, pi. 1, represents a filament of the American plant magnified 1250 dia- 

 meters. The color and form are closely counterfeited, but the characteristic sepa- 

 ration of the endochrome into parts at the joints is decidedly exaggerated. 



O. neglecta, Wood. 



0. trichomatibus modice brevibus, aut dilute purpuraceo-plumbeis aut plumbeo-cinereis, pler- 

 umque.rectis, aut stratum mucosum atro-purpureum baud distincte radiante formantibus, aut 

 in strato gelatinoso baud radiante subplurabeo dispersis et cum algis aliis intermixtis, rare 

 oseillantibus sed lente sese moventibus ; articulis diametro fere 4 plo brevioribus ; dissepi- 

 mentis plerumque hand granulosis, rare indistincte granulosis; apiculo obtuse rotundato, 

 interdum breviter nonnihil attenuato. 



Syn.—O. neglecta, Wood, Prodromus, Proc. Amer. Philos. Soc, 1869, 124. 



Diam.—j-g\^" = .0066. 



Sab. — In stagnis prope Philadelphia, 



Filaments rather short, of a dilute purplish-lead color, or leaden-gray, generally straight, either 

 forming a mucous, blackish-purple stratum without marked rays, or diffused with other algae 

 in a gelatinous mass, rarely oscillating but gliding ; articles about four times shorter than 

 broad ; joints for the most part not granulate, rarely indistinctly granulate ; ends obtusely 

 rounded, occasionally short, somewhat attenuate. 



Remarks. — I have found this plant in the shallow ditches along the track of the 

 Norristown Railroad above Manayunk, growing in two diff'erent ways. In the one 

 it forms a distinct, soft, gelatinous, floating stratum of a very dark purplish color, 

 consisting of nothing but interwoven filaments, and provided with long rays. In 

 the other, the plant is largely mixed with diatoms and other algae into a thick, 

 gelatinous stratum without rays, whose color is a dirty slaty tint, which, however, 

 is not all distinctive, and often varies as the proportion of the different constituents 

 varies. The color of the single filaments is a slaty, almost neutral tint. The 

 , cytioplasm is remarkable for the numerous very minute spots more transparent and 

 with less color than the surrounding parts. Th-e ends of the filaments are often 

 abruptly obtuse, frequently however there is a very short taper. Motion does not 

 appear to be very active, and seems especially to be gliding, rather than a bend- 

 ing to and fro of filaments. 



Fig. 5a, pi. 2, is an outline drawing of a filament magnified 450 diameters ; 56 

 is a portion of a filament. 



O. imperator, Wood. 



0. in strato mucoso, plerumque natante, olivaceo-atro, longe radiante; trichomatibus rectis aut 

 subrectis, tranquillis, dilute viridibus vel saturate olivaceis, haud oseillantibus, sed ambulan- 

 tibus; apiculis nonnihil attenuatis, late rotundatis vel subtruncatis, curva.tis; articulis diarhe- 

 tro 5-12 plo brevioribua, ad genicula indistincte contractis ; cytioplasmate homogeneo, 

 olivaceo-viride ; vaginis firmis, ad genicula distincte transverse striatis. 



Syn. — 0. imperator, WooDj Prodromus, Proc. Amer. Philos. Soc, 1869, 124. 

 Biam.— .002" . 



