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



cells, which dissolve into oblong, oval, transparent immotile.spermato- 

 zoids (Sporidia Ag.). 



2. Cystocarpia Ktz., or Pistillidia, formed of somewhat moniliform sori, 

 which are evolved from a generally cortical placenta, and are naked or 

 surrounded by a mucilaginous cuticle or involucre, and finally emit 

 numerous immotile spores (polyspores), which quickly germinate. The 

 fecundation of the cystocarpia occurs in their primordial state by con- 

 tact of the spermatia with a piliform organ known as trichogonia. 



3. Tetrasporangia formed of single, greatly swollen cortical cells, be- 

 coming cruciately quadrilocular by division of the "primordial utricle; in 

 each loculus (secundary or sister cells] a single spore (tetrasporc) forms, 

 which germinates without fecundation. . 



FAMILY PORPHYRACE^E. 



Thallus mucoso-rnembranaceus, foliaceus vcl filamcntosus, e ccllularum seriebus vel strato uuico 

 formatus, plerumque purpurascens, valde lubricus. 



Vcgetatio fit cellularum divisione in duas vel omnes directiones rcpetita. 



Propagatio fit tetrasporis. Cystocarpia nondum observata. 



Thallus mucous-membranous, foliaceous or filamentous, formed of cells in series or in a single stra- 

 tum, mostly purplish, very slippery. 



Growth taking place by repeated division of the cells in two or all directions. 



Propagation by means of tetraspores. Cystocarps not yet observed. 



Remarks. The only species of this family as yet observed in North America 

 can hardly be said to have a definite thallus. They are rather multitudes of cells 

 heaped together and closely attached to one another into a shapeless expanded 

 mass. 



Genus POKPHRYDIUM, NAEG. C1849). 



Thallus mucoso-membranaceus, subcrustaceus, longe lateque expansus, e cellulis globosis vel 

 polyedricis compositus. Propagatio adhuc ignota. 



Thallus mucous-membranous, subcrustaceous, long and widely expanded, composed of globose or 

 polyhedral cells. Propagation unknown. 



P. crueEitum, (Ao.) NAEG. 



P. thallo saturate purpuro-sanguineo, lubrico ; cellulis anguloso-rotundatis. (R.) 

 Diam 0.00027" 0.00035". (R.) 

 Hob. New York. 



Syn. P. cruentum, (AGARD.) NAEGEL. RABENHORST, Flora Europ. Algarum, Sect. III. 

 p. 39?. 



Thallus deep crimson purple, slippery ; cells angled and rounded. 



Remarks. The only specimen I have seen of this species was a little speck, 

 adherent to a bone picked up on Governor's Island, in New York Harbor. It is 

 very probable that it was a recent arrival, brought over, perchance, by some emi- 

 grant. For it I am indebted to Dr. Billings, TJ. S. A. The description and 



