FRESII-WATER ALGJE OF THE UNITED STATES. 21 



Hab. — In stagnis prope Pliiladelphia. 



0. occurring in an olive-black, niiicous stratum, mostly swimming and with long ra_ys ; filaments 

 straight or straightisli, light-green or deep-olive, tranquil, not oscillating, but moving with a 

 gliding motion ; ends somewhat attenuate, broadly rounded or subtruncatc, curved ; articles 

 5-12 times shorter than broad, slightly contracted at the joints; cytioplasm homogeneous, 

 olive-green ; sheaths firm, distinctly transversely grooved at the joints. 



Eemarls. — The strata of this species are often of great extent, and resemble 

 more masses of spirogyra than of tlie ordinary oscillatoria. They are very loose in 

 texture ajid are very slimy, whilst their edges are fringed by the long tranquil 

 rays. In certain conditions of growth, the endochrome of the filaments is so dense 

 as to render them very opaque and the articulations very obscure. The sheaths 

 when emptied show the marks of the joints very distinctly ; but, at times, when 

 gorged with cytioplasm, scarcely can the sheath itself be seen. The color of the 

 filament is also affected by the state of the protoplasm, so that it varies from a 

 lightish-green with an olive tint to a very decided dark olive. This species seems 

 to be closely allied to the European 0. prlnceps, from which, however, it differs in 

 its motion, which is always very slow and merely gliding, its color, the distance of 

 the dissepiments, and the much longer curvature of the ends. It grows everywhere 

 in the ditches around the city ; when mature, generally floating upon the surface 

 with an adherent under-stratum of dirt, but, in its earlier history, often adhering 

 to the bottom. 



Fig. 6a, pi. 1, is a drawing of the end of a filament; fig. 6?), represents a small 

 fragment of a filament, showing the tendency to take a roundish or barrel shape ; 

 much of the endochrome has been squeezed out by the injury which has broken 

 the filaments. 



Genus CIITIIOXOBLxlSTUS, Ktz. 



Phormidii trichomata fasciatira congesta et vagina communi mucosa apice clausa vel aporta inclusa. 

 Tales fasciculi numerosi in stratum (quasi thallum) gelatinosum, passim amoso-divisum aggrcgati. 

 Vaginte communes achromatica;, sa^pe laraellosa;, plus minus ampliata;, rarius indistinct^ et subnulla', 

 evacuatae, pleruraque valde intumescentes. Trichomata Phormidii mode oscillantia, articulata et 

 vaginata, rigida, recta vel ])arum curvula, in fasciculos funifornics plus minus dense contorta, apice 

 soluta et divaricata. Cellulas propagatorias observare mihi contigit. (II.) 



Filaments fasciately placed together and included in a common mucous sheath with open or shut 

 apex. A number of these fasciculi aggregated in a gelatinous stratum (pseudothallus), whicli is 

 gelatinous, and here and there ramosely divaricate. Common sheath colorless, often lamellate, more 

 or less enlarged, rarely indistinct and nearly wanting, when empty mostly markedly intumescent. 

 Filaments oscillating like to those of Phormidium, articulate and vaginate, rigid, straight, or a little 

 curved, more or less densely entangled into cord-like fasciculi, with the apex dissolved and dis- 

 severed. 



Cli. repens, Ktz. 



Ch. terrestris, strato plus minus expanso, saturate ajrugineo-chalybeo aut olivaceo-fuscescente, 

 mucoso-membranaceo ; tricboniatibus fequalibus in fasciculos filiformes, soepo valde elon- 

 gatos, e vagina; communis apertura pcnicillatim cxsertos congestis; articulis diametro iequali- 

 bus dissppimentis granulatis, apicnlo obtuse recto. (R.) 

 Species, mihi ignota. 



