208 FRESn-WATEll A L G .E OF TUE UNITED STATES. 



Eemarks. In this form there are almost always numerous little clusters of branch- 

 lets, "■ro\vin<'- iuiniediately from the main stem or large branches; such clusters are 

 more ri<nd, more open, more broadly ovate, and less markedly piliferous than tho 

 others. 



D. pliiinosa, (Vaucher) Aqardh. 



D. filis raiuisque primariis byalinis, plcnimqne 5V'" = O-OOITO" crassis; articulis diamotro 

 sequalibus vel dimidio brevioribus, rarius paulo lougioribus, geuiculis vix aut modice cun- 

 strictis, fasciis chloropliyllosis aiigustis Isele viridibus ; articulis infcrioribus ramulorum dia- 

 metro ( lis'" — 35s'") a^qualibus vol subduplo lougioribus, psene torulosis, superioribus cylin- 

 dricis ad ttI^"' attenualis, diamctro duple triplo-quiutuplo lougioribus, plerumque nou pili- 

 feris ; ramulorum fasciculis dense 7-amellosis, elongatis, acute lanceolatis, erecto-subap- 

 pressi'.s. (H. ) 



Sijn. Dr. jjlumosa, (Vaucuer) Aoakdu. Rabenhorst, Flora Europ. Algarum, Sect. III. 



p. 382. 



JIab. — In rivulis et aquis quictia 



Filament and primary branches hyaline, mostly g^^j'" = 0.001Y9" in diameter; articles as long as 

 broad or one-half shorter, rarely a little longer, scarcely or slightly constricted at the joiuts, 

 chloropliyl fascia bright green, narrow ; lower articles of the branches about as long as 

 broad (155"' — 553'") or nearly twice as long, somewhat torulose, the upper ones cylindrical, 

 as small as 553'", two to five times longer than broad, mostly not piliferous ; fascicles of 

 bi'anchcs denst'b/ branched, elongate, acutely lanceolate, actually subappressed. 



Remarks. — 1 have found a iJra^x/rwaZJta frequently, which I believe to represent 

 the European D. plumosa. As I have preserved, however, no specimens or 

 descriptions, I have simply copied the description of Prof. Rabenhorst. 



D. Billing;!!)!!, Wood. 



D. valde gelatinosa ; filis et ramis primariis aehrois ad ^%%ts" crassis, sparsissime ramosis, 

 articulis diametro 2-6 plo lougioribus, srepe medio valde tumidis ; fasciis chlorophyllis dilute 

 viridibus, siepe nullis aut subnullis ; ramulorum fasciculis distantibus, late ovalibus vel late 

 triangularibus, alternantibus vel oppositis vel triplice verticellatis, sparse ramosis, patentissi- 

 mis ; ramulis pilis longissimis robustis terminalibus instructis ; oosporis globosis, monilifurme 

 conjuQctis ; sporodermate crasso. 



Sijn.—D. Billingsii, Wood, Proc. Am. Philos. Soc, 1869, p. 143. 



Hab. — In aquis quietis, prope Philadelphia. 



Frond very gelatinous, filament and primary branches attaining a diameter of ^J^", very 

 sparsely branched, their articles 2-6 times longer than broad, often very much swollen in 

 the middle ; chlorophyl band light green, frequently almost or entirely wanting ; fascicles 

 of branches distant, broadly oval or triangular, alternate, opposite, or in whorls of three, 

 very open; ultimate branehlets terminating in a long, robust, hyaline hair; resting spores 

 globose, with thick walls, arranged in long moniliform sometimes branched filaments. 



Remarhs. — I found this plant about the middle of March, 1869, floating on the 

 surface of a little pool in the woods near Chelten Hills, a few miles north of 

 Philadelphia. To the naked eye it appears as a gelatinous mass, resembling a 

 Tetrafipora, but when closely examined this translucent jelly is seen to be filled 

 with rather distant greenish points, which are the little clusters of branches. The 

 largest specimens I have seen had attained a length of nearly two inches. The 

 filaments are very transparent and have the branches placed at long intervals. 



