FRESH-WATER ALQAi OF TUE UNITED STATES. 39 



lulls perdurantibus interjectis, articulis vegetativis subaequalibus, utroque polo puncliforme 

 iucrassatis, subsphsericis; sporis subsphaericis. 



Syn. — A. gigantea, Wood, Prodromus, Proc. Amur. Philos. Soc, 18G9, 145. 



Eab. — In stagnis natante, prope Philadelphia. 



Diavi. — Artie, vegetat. max. ^^^^^. Utterocysts j^'j^ = .0005. Spor. lat. T^^Vuts = Loug. 

 „Vtr = -001. 



Thallus wanting ; filaments oceurring floating singly on water or in great numbers, straight, 

 but in the young state often spirally convolute ; articles mostly subglobose, closely connected, 

 granular, heterocysts subspherical, interstitial, a very little larger than the vegetative cells, 

 thickened at each end iu a punctiform manner; spore subspherical. 



Remarlis. — This plant was found by myself, late in the summer, floating upon a 

 brick-pond below the city, forming a part of a thick, dirty-green, " pea-soup 

 colored," almost pulverulent scum. The filaments, though occasionally in great 

 numbers, were never, that I saw, joined together by any jelly so as to form a frond. 



Fig. 5, pi. 3, represents a short filament of this species magnified 750 diameters. 



Genus CYLINDROSPERMUM, Ktz. 



Sporae ante cellulam tcrminalem ortae. 



Spore developing from the next to the terminal cell. 



C. niiniitum, Wood. 



C. trichomatibus dilute terugineis, plerumque flexuoso-curvatis et intricatis, interdum subrectis ; 

 articulis cylindricis, ad genicula plus minus constrictis, homogeneis vel granulatis; cellulis 

 perdurantibus terminalibus, hirsutis, globosis; sporis cllipticis, diametro 2 — 3 plo longioribus, 

 subtilissime granulatis. 



Syn. — C. minutum, Wood, Prodromus, Proc. Amcr. Philos. Soc, 18G9, 126. 



X>jam.— Artie. ^^VV ; spor. long. ^■^^■^" ; transv. j^Vo"- 



3ah. — In stagnis prope Philadelphia. 



Filaments light seruginous-green, generally curved and intricate, sometimes straightish ; articles 

 cylindrical, more or less constricted at the joints, homogeneous or granulate; heterocysts 

 terminal, hirsute, globose; spores elliptical, 2 — 3 times longer than broad, very minutely 

 granulate. 



Remarlcs. — This species was found by myself at Spring Garden, New Jersey. 

 With a number of other algae it formed a ferruginous-brown gelatinous mass, 

 growing in a deep, shaded, very stagnant pool. In most instances the filaments 

 were closely interwoven, and sometimes formed minute greenish balls, just large 

 enough to be visible to the unassisted eye. In other instances they were mixed 

 up with various algae in little indefinite masses. There is apparently a stage in 

 the life of the plant, when it consists of a single filament enclosed in a little cap- 

 sule, for mixed in with the rest of the gelatinous sctmi were little microscopic, sub- 

 globose masses, with a firm outer periderm and a single filament coiled up in the 

 centre. The color of the filaments was generally a faint bluish-green, sometimes, 

 however, with a yellowish tint. The spores were decidedly yellowish. 



Fig. 6, pi. 2, represents a fragment of a filament with the spore magnified 800 

 diameters. 



