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



Absecom, Perth Amboy, and low grounds generally, New 

 Jersey. 



Syn. Wiizo. riparium, Harv. ; RMzo. obtusangulum, Kg.; Con- 

 ferva riparia, Ag. ; Zygnema litoreum, Kg. 



Plate CXXII, figs. 5, 6, 7. 



EHIZOCLONIUM MAJOR, Wolle. 



Stratum dark green, filaments densely interwoven, some- 

 what rigid, lateral processes short, numerous, cell contents 

 3-4 parted ; diameter of articulations 33-48 //, equal, to 

 twice as long ; cell membrane firm. 



This finely developed, large plant, was found growing on 

 the wooden structure of the docks at Perth Amboy, New 

 Jersey. It is nearest Rhizo. pannosum, Aresch., and may 

 be a variety of it. It differs in having twice the diameter, 

 in the character of the rootlets, and in habitat. 



Plate CXXII, figs. 1-4. 



% 



Order III SIPHONED. 



Plants in vegetative state, unicellular, often prominently 

 branched, tubular or utricle-shaped ; dwellers in water, and in 

 air. 



This Order is represented by only two genera, widely different 

 in appearance and in their mode of propagation. The one has 

 sexual fertilization, and asexual zoospores ; the other has sexual 

 oospores and asexual zoospores, beside other mode of propaga- 

 tion by rnicrogonidia. 



Family X. VA UCHEEIA GE^. 



Filaments caespitose, green, rather robust, unicellular, land 

 and water dwellers. 



A plant consists of a single, elongated, tubular filament, ordi- 

 narily more or less branched. The chlorophyl rather evenly 

 distributed on the inside of the walls of the tubes with green 

 granules and minute oil drops imbedded. 



Propagation either sexual, by oospores fecundated by sper- 

 matozoids, or non-sexual by zoospores. 



Sporangium terminal, formed by the globosely clavate swelling 

 of the tip of the thallus, cut off by a septum ; contents dark 

 green, at length enclosing one large zoospore. 



