20 FRESH- WATER ALG^E 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. ncglectn, WOOD. 



O. 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 subplumbeo dispersis et cum algis aliis intermixtis, rare 

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

 mentis plerumque baud granulosis, rare indistincte granulosis; apiculo obtuse rotuiidato, 

 interdum breviter nonnibil attenuate. 



Syn. 0. neglecta, WOOD, Prodromus, Proc. Amer. Philos. Soc., 1869, 124. 



Diam.f&a" = .0066. 



Hab. 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 algte 

 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. 



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

 Norristown Railroad above Manayunk, growing in two different 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. The ends of the filaments are often 

 abruptly obtuse, frequently however there is a very short taper. Motion docs 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. 



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

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

 tibus; apiculis nonnihil attenuatis, late rotundatis vel subtruncatis, curvatis; articulis diame- 

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

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



Syn.O. imperator, WOOD, Prodromus, Proc. Araer. Philos. Soc., 1869, 124. 

 Diam. .002". 



