FRESH-WATER ALO.E OF THE UNITED STATES. sj 



outer coat. The lateral transparent spot in the cells is mostly very evident, some- 

 times it is wanting, however. Occasionally then- is a very distinct blackish "eye 

 spot." The threads which join the cells arc very delicate, and I have never been 

 alile to absolutely demonstrate their meeting in the centre of the frond, although 

 I believe they do so. In mounted specimens, even when preserved in carbolic 

 acid water, they disappear after a time. I have never seen zoospores or any other 

 reproductive bodies. 



Genus RHAPHIDIUM, KTZ. 



.ulir fu.-iformes vel cylindracete, utrinquo (plernmque) sensim srnsitnquc cuspidate vel acumi- 

 nate, rarius uliiu.-ata*, rectw vel vnrie curvate, singule, gemine Tel fasciculatim aggregate, medio 



-utiiii vd radiatira conjunct*, rarius bine sub polls lateraliter conncxe, cetcrura liber*. 



lermu tcnue, hfvo. ('yti"i>la.sina viridc, subtiliter granulosum, locello pallidiori vel acbroo, 

 ceutrali, rarius lateral!, preditum. Cellularutu divisio ad uiiam directionem. (R.) 



Cells fusiform or cylindrical, generally very gradually cuspidate or acuminate at the ends, rarely 

 obtuse, straight or variously curved, single, geminate, or fasciculately aggregate, decussate in the 

 centre or radiately conjoined, rarely two laterally united at the end, other cells free. Cytioderm 

 thin, smooth. Cytioplasm green, very finely granular, furnished with a central or rarely lateral 

 transparent vacnole. Division of the cells occurring only in one direction. 



R. polyiiiorphiini, FRESIM. 



K. crllulis rectis vel varie curvatis, singulis, vel 2-4-8-16 fasciculatim collocatis, gracilibns, 

 sepe gracillimis, nonnunquam medio paullum tnrgidia, subvcntricosis, nonnunquam panllum 

 constrictis, apices versis, seu.sim attenuatis, acutissimis. 



,,,._ T /,"=. 00013". 



Sy,i. Jt. polymorphism, FRKSKN., RABENOORST, Flora Europ. Algarum, Sect. III. p. 44. 

 Hub. Prope Philadelphia, Wood- 

 Cells straight or variously curved, single or 2-48-16 faacicnlately joined together, slender, 



often exceedingly so ; sometimes slightly turgid in the centre, Bubventricosc, sometimes 



slightly constricted ; the apices gradually attenuate, very acute. 



Var. fhlcntuiii. 



< Yllnlis fusif'irniibiis. gracillibus, utroque fine acutissirao cnspidatia, curvatis vel scmilnnaribug, 

 416 fasciculatim congregatis. 



Syn. Ankisirodesmus falcatus. (CoRDA.) RABENHOROT, Flora Enrop. Algarum, Sect. III. 



p. 45. 

 Hob. South Carolina, Georgia, Florida, Rhode Island. (Bailey.) 



Cells fusiform, slender, at each end very acutely cuspidate, curved or semilunar, 4-16 fascicn- 

 lately congregate 



Remark, Fig. 3, pi. 7, represents different forms of R. pdymorphum. 



FAMILY PROTOCOCCACELE. 



Algic unicellnlares scnsu strictissimo, chlorophyllosa, et vegetatione terminal! et ramificatione 

 vera carentes, sine cellularum generatione vegetativa. Vivnnt aut singulee, segregatae aut in farai- 

 lia conaociate. Harum familiarnm cellule nnraero ant indefinite semper se angentes (turn sensu 

 vero familiie nomen fcrnnt), aut definite, se non augcnUs (qne coenobium dicuntur). 



