40 RHODOMELACE^. v. 



the North American ones. I found it on the purple, whip-hke Gorgonia so com- 

 mon at Key West. 



12. PoLTSiPHONiA Olneyi, Harv.; tufts dense, silky, flaccid, purple-brown ; fila- 

 ments capillary below, byssoid above, decompound, excessively branched ; branches 

 very patent or divaricate, many times compounded, gradually attenuated, more or 

 less beset with scattered, slender, spinelike ramuli ; articulations very variable in 

 lensth, in the lai'ger branches from two to six times, in the lesser branches and 

 ramuli once and half to twice as long as broad ; conceptacles ovate, subsessile ; 

 tetraspores in distorted ramuli. Harv. in Obiey's List of Rhode Island Plants^ 

 Proceed. Prov. Frank. Soc, Apl. 1847. (Tab. XVII. B.) 



Hab. On Zostera, &c. Halifax, W. H. H. Nantucket, Dr. Durkee. Providence, 

 Rhode Island, (1846) Mr. S. T. Olney. Greenport, Long Island, Prof. Bailey and 

 W. H. H.(v.v.) 



Tufts from three to five inches long, dense, soft and silky. Filaments as thick as 

 human hair, or sometimes twice as thick at the base, where they are also of a firm 

 substance ; soon becoming thinner, and passing off above into excessively fine, 

 byssoid ramuli, much branched from the base without regular order ; the bi'anches 

 many times compounded by alternate or unilateral ramification. Branches more or 

 less furnished with lateral spinelike, scattered ramuli, from a line to a quarter inch 

 in length. The lower divisions of the stem and branches are very patent, some- 

 times widely divaricating, the upper more erect, with narrower angles. A cross 

 section of the stem, or of one of the larger branches near the base, shows four large 

 primary tubes surrounding a central cavity, and four secondaries of small size 

 alternating with them. The internodes are very variable in length in different spe- 

 cimens ; those of the stem and larger branches are frequently not more than twice 

 as long as broad, but are sometimes four or even six times their length ; those of 

 tlie lesser branches and ramuli are more uniformly short. Conceptacles ovate, abun- 

 dantly scattered over the lesser branches. Colour a rich purple brown, more or less 

 intense. Substance soft and lubricous. It adheres very closely to paper in drying. 



This species has many characters in common with the following, but is a more 

 slender plant, much softer and more lubricous in substance, with longer inter- 

 nodes, longer, more filiform and much less abundant ramuli, &c. It must be 

 allowed, however, that most of these characters are variable. The length of the 

 internodes is particularly so, the first specimens which I received from Mr. Olney, 

 and on which I founded the species, having them uuiforndy short ; while others, 

 collected in the same locality, but at a different season, have them often of the 

 great length shown at fig. 5. 



Plate XVII. B. Fig. 1, a frond of Polysiphonia Olneyi., removed from the tuft, 

 the natural size. Fig. 2, part of a branch from the same ; fig. 3, a small portion of 

 the branch with ramulus ; fig. 4, part of a branch from another specimen ; fig. 5, 

 one of the longer internodes from the same ; fig. 6, a conceptacle ; fig. 7, transverse 

 section of the stem ; the latter figures more or less magnified. 



