V. SPH.EROCOCCOIDE.'E. 9I 



IV. HriiENENA. Frond ribless, traversed by numerous, sul)parallel, anastomosing 

 veins. Sori linear, between the veins. 



Y. NiTOPHYLLmi. Frond ribless, either veinless or traversed by obsolete, slender, 

 branching, irregular veins. Sori roundish, scattered. 



Tribe 2. Sph^rococce^. Frond flat, compressed, or cylindrical, cartilaginous or 

 coriaceous, the surface cells roundish, very minute. Placenta conical, projecting 

 far into the conceptacular cavity. Tetraspores mostly dispersed among the surface 

 cells. 



* Tetraspores oblong^ transversely divided (zonate). 



VI. Calliblepharis. Frond flat, irregularly cleft, fringed Tvith marginal lobes. 



* * Tetraspores cruciate or triangularly divided. 

 YII. Gracilaria. Frond terete, compressed or flat. 



VIII. Corallopsis. Frond constricted at regular intervals or nodoso-articulate. 



I. GRINNELLIA. (Nov. Gen.) 



Frond rosy red, leaf-like, delicately membranaceous, areolated, symmetrical, 

 traver.sed by a slender, percurrent midrib. Conceptacles scattered over the surface 

 of the membrane, bottle-shaped, with a prominent orifice : placenta basal, somewhat 

 l)rominent, crowned with a pulvinate tuft of subdichotomous spore-threads, whose 

 terminal cells are earliest ripened. Spores elliptic-oblong or roundish. I'etraspores 

 tripartite, immersed in scattered, shapeless, cellular warts. 



The remarkable plant Avhich I propose as the type of this genus is peculiar to 

 the eastern shores of North America, along which it ranges from Cape Cod to New 

 Jersey. It abounds in Long Island Sound and New York Harbour, where it con- 

 stitutes one of the most ornamental features of the submarine flora. It was ori- 

 ginally described by the elder Agardh as a species of De/esseria, a genus which, as 

 then understood, comprehended almost every Alga with a red, membranous, leaf- 

 like frond, and included also within its limits Plocamium and Stenogramme. From 

 the restricted genus Delesseria it is readily known by the position of the concep- 

 tacles, which organs in Delesseria are invariably placed cither on the principal 

 midrib or on one of its lateral branches. To Nitophyllum {Aglaiophyllum, Mont.) 



N 2 



