182 FRESII-WATER ALG^ OF THE UNITED STATES. 



Multicellular, cliloropliyllous alga;, membrauaceous or filamentous, furnished with or destitute of 

 brauches. Propagated by oospores or zoospores, never by conjugation. 



Family ULVACE^. 



Thallus membranacens vel foliaceus, vel filiformis (Schizomeris?) rarius crustaceus, e cellularum 

 strato unieo formatus, aut expansus aut tubuloso- vel vesiculoso-concrotus. 



I'ropogatio fit zoogonidiis, cytioplasmatis divisione repetita ortis. Zoogonidia oblonga, polo 

 aiitico eiliis vel binis vel ternis vel quarternis iustructa. 



Thallus membranous or foliaceous, rarely crustaceous, composed of a single stratum of cells, either 

 expanded or tubularly or vesicularly concreted. 



Propagation by means of zoogonidia, formed by the repeated division of the cytioplasra. Zoogoni- 

 dia oblong, furnished with two, three, or four cilia at the anterior end. 



Genus PROTODERMA, Ktz. 



Thallus crustaceus, indeterminatus, substrate arete adherens, e cellulis anguloso-rotundatis, 

 irregulariter ordinatis, arete conuexis compositus. 



Propagatio ignota. 



Thallus crustaceous, indeterminate, closely adherent to the substratum, composed of closely eon- 

 joined irregularly arranged angularly rounded cells. 



Propagation unknown. 



P. viride, Ktz. 



P. viride, lubricum. 



Syn. — P. viride, Kutzing. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 307. 



Hab. — In aquario ; Wood. 



Green ; slippery. 



Remark. — I have seen a plant, which I take to be this species, growing on the 

 glass and on pebbles in the aquarium of my friend, Dr. Fricke. 



Genus ULVA, Linn. 



Thallus nicmbranaceus, plane c.xpansus, angustus vel latus, nonnunquam latissimus, magis minusve 

 undulato- crispatus, sa;pe laciniatus, baud raro perforatus, e cellularum strato uiiico formatus, callo 

 disciformi parvo affixus, cetate provecta saepe libere natans. Cellulce anguloso-rotundatse, coeloplas 

 matica;, parenchymatice conncxse. 



Vegetatio cellularum divisione in duas directiones repetitia. Propogatio fit zoogonidiis, in cel- 

 lulis quibusdam cytioplasmatis divisione 4, 8-16 ortis, eiliis vibratoriis quaternis longitudine cor- 

 poris longitudineni vix superantibus instructis. 



Thallus membranous, expanded, narrow or broad, sometimes very broad, more or less undulately 

 curled or crisped, often laciniate, not rarely perforate, formed of a single stratum of cells, fastened 

 by a small discoid thickened portion, in advanced age often swimming free. Cells angularly glo- 

 bose, joined into a sort of parenchyma. 



Growth occurring by the repeated division of the cells in two directions. Propagation by 

 zoospores, 4-8-1 fi of which are formed at once by a division of the endochrome of certain cells, 

 and are furnished with four vibratile cilia scarcely longer than the body. 



tJ. merisiiiopedioides, Wood. 



U. ampla, mcmbranacea, late expansa, dilute viridis, tenuis, radiatim et enorniiter plicata, ambitu 

 sajpe subrotundata; niargine undulato, interdum subcrcnato ; cellulis enormiter ovalibus vol 

 angularibus, nnclco destitntis, quarternariis et in familias Merismopediarum modo obscure 

 a.ssociatis. 



7)mm.— Cell. max. „i5iTTy" = .00041', plerumqno yjlno" — xugi^o" = .00016' - 00025. 



