120 FRESH-WATER ALG^E OF THE UNITED STATES. 



Docidium nodulosum, BREB. RALFS. British Desmidife, p. 155. 

 Closlerium trabecula, BAILEY. American Journal of Science, 1841. 



Hob. In aquis quietis, South Carolina ; Georgia ; Florida ; Rhode Island ; Bailey. Pennsyl- 

 vania ; New Jersey ; Wood. 



(Docidium. nodulosum.') Frond very stout, the thickened sutures forming a projecting rim ; 

 segments four to six times as long as broad, scarcely attenuated, regularly inflated at intervals 

 so as to form an undulated margin, the basal inflation the most prominent, the others, as they 

 approach the ends, less so, where they are indistinct or wanting ; ends entire ; e. f. coarsely 

 punctate. L. g 1 ^ ". B. 55-5". Archer. Pritchard's Infusoria. 



Remarks. I have found this species in " Shepherd's Mill Pond," near Greenwich, 

 Cumberland County, New Jersey, and also in a Spring in the Philadelphia Park, 

 near Columbia bridge. 



Fig. 1, pi. 21, represents the outline of a frond of this species magnified 160 

 diameters. 



P. Clavatnin, (Kiz.) DE BARY. 



P. subcylindraceum, multoties (16-24) longius quam latum, ad utrumque polum sensim incras- 

 satum, subclavatum, apicibus late truncatis ; cytiodermate firmo achroo, dense et irregulariter 

 granulato-punctato. (R.) Species mihi ignola. 



Diam.M&x. 0.00165" 0.00147" ; min. = 0.0010" 0.00092". (R.) 



Syn. P. clavalum, (Kiz.) DE BARY. RABENHORST, Flora Europ. Algarum, Sect. III. p. 141. 

 Docidium clavatum, KUTZING. RALFS, British Desmidise. ARCHER. Pritchard's Infusoria. 

 Hob. South Carolina ; Georgia ; Bailey. 



Frond slender, suture scarcely prominent, segments eight to ten times as long as broad, slightly 

 clavate near the ends, and ultimately somewhat attenuated, basal inflation sometimes solitary, 

 sometimes having another slight one above it; ends entire; e. f. punctate. L. ff y. B. ^iV'- 



P. undulatnm, (BAILEY.) 



D. laeve, gracile cylindricum, undulatum, latitudine 18-20plolongins, medio modice constrictum ; 



cruribus et basi et apice truncatis et crenatis. (R.) Species mihi ignota. 

 Syn. Docidium undulatum, BAILEY. Micros. Observ. p. 36. 

 Hob. Florida, Bailey. 

 " Segments eight to ten times longer than broad, constricted six to eight times at regular intervals 



throughout their entire length, with the base and ends crenate, smaller than D. nodulosum, 



BREB., with more frequent and deeper constrictions. The same characters distinguish it from 



D. nodosum and D. constrictum." 



P. nodosum, (BAILEY.) 



D. validissimum, undulatum, spinulis eparsis hirsutum, medio valde constrictum, diametro 8-10 

 plo longius ; cruribus e basi dilatata leviter attenuatis 4-undatis, apicibus quasi productis, 

 latissime truncatis; locello apicali ratione parvo, rotundo, corpusculis paucis (ut videtur) 

 repleto. (R.) (Species mihi ignota.) 



Syn. Docidium nodosum, BAILEY. Micr. Observ., pi. 1, fig. 4. RALFS, British Desmids, 

 p 218. 



Hab. United States ; Bailey. 



"Frond stout; segments with four prominent nodes separated by constrictions; end view 

 crenate. An end view shows that each node is not a simple swelling, but really formed by 

 whorls of tubercles. 'This species is easily recognized by the deep indentations in its out- 

 line, corresponding to the constrictions which separate the transverse rows of knob-like pro- 

 jections. It is one of the largest species in the genus,' Bailey." Ralfa. 



