122 FRESH-WATER A L G JK OF T II E UNITED STATES. 



T. gracille, BAILEY. 



T. cellulis subcj'lindricis, utroque fine vix angustatis, gracillimis, diametro 25-30 plo longi- 

 oribus ; processibus lateralibus brevibus, conicis. 



Diam. Cum process. TS 8 SW " = .008"; sine proc. T5 f^" = .0006". 



Syn T. gracille, BAILEY, Smithsonian Contributions. 



Docidium pristidse, HOBSON, Magazine Natural History, v. p. 168. 

 Pleurolsenium yracile, RABENUOKST, Flora Europ. Algar., Sect. III. p. 144. 



Hab. In iisdem cum antecedente locis. 



Subcylindrical, scarcely narrowed at the ends, 25-30 times longer than broad ; lateral processes, 

 short, conical. 



Genus SPIROT^NIA, BREB. 



Cellulae rectae, cylindrical vel subfusiformes, saepe in muco gelatinoso aggregates, medio haud con- 

 strictss, utroque polo rotundatse vel acuminatae. Cytioplasma chlorophyllaceum in laruinis spiralibus 

 dispositum. 



Cells straight, cylindrical or subfusiform, often aggregated in a gelatinous mucus, not constricted 

 in the middle, rounded or acuminate at each end. Chlorophyllous cytioplasm arranged in spiral 

 lamina. 



Sp. bryophila, (BREB.) RABENHORST. 



Sp. mimina, bryophila ; cellulis in gclatina matricali consociatis, oblongo-cylindricis, rectis vel 

 subcurvatis, bis vel ter longioribus quarn latis, utroque polo rotundatis ; lamina chlorophyl- 

 lacca singnla anfractu l-2. 



Z>tam. 3^7" = 0033" (0.00024" .00029". R.) 



Syn. Spirotsenia bryophila, (BREB.) RABENUORST, Flora Europ. Algarum, Sect. III. p. 146. 



Hab. Prope Philadelphia ; Wood. 



" (S. muscicola (De Bary)) Frond cylindrical two to four times as long as broad, ends rounded; 

 endochrome a single, broad, smoothly defined, widely wound spiral baud, its revolutions very 

 few (one or two}." (A.) 



Remarks. I found this beautiful little desmid on the North Pennsylvania Rail- 

 road, near Chelten Hills, growing amongst some mosses which were kept con- 

 stantly wet by overhanging dripping rocks. It formed little transparent masses of 

 almost colorless jelly looking much like drops of dew. It agrees well with the 

 descriptions of the European form, except that there were generally from 2-2| 

 turns of the spiral, and the cells exceed somewhat the measurements of Prof. 

 Rabenhorst. The cells are closely placed in the jelly. 



Fig. 10, pi. 12, represents some plants of this species. 



Sp. condensata, (BREB ) RABENHORST. 



Sp. cellulis cylindraceis, rectis (vel leviter curvatis) octies vel decies longioribus quam latis, 

 utroque polo rotundatis; lamiuis chlorophyll, singulis, anfractibus subarctis (plerumque 8-12). 



Diam. 0.00075". 



Syn. Sp. condensata, (BREB.) RABENHORST, Flora Europ. Algarum, Sect. III. p. 146. 



Hab. Florida ; Rhode Island ; Bailey. Pennsylvania ; Wood. 



Frond cylindrical, two to four times as long as broad, ends rounded ; endochrome a single, 

 broad, closely wound spiral band, its revolutions numerous. L. ?&*" Br. -HTIB"- Archer. 

 Pritchard's Infusoria. 



