SPOROCHNACE^.— Aetheocladia. 75 



Synopsis of the Noeth Ameeican Geneea. 



I. Aetheocladia. Frond pinnate, filiform, nodose, hollow ; the tube articulated 



within. Nodes whorled with delicate filaments. 



II. Desmaeestia. Frond pinnate, either filiform, compressed, or flat, solid. 



III. Chnoospoea. Frond dichotomous, flat. 



I. ARTHROCLADIA, Duhy. 



Frond cylindrical, pinnated, traversed by a wide, empty tube which is interrupted 

 at short intervals by transverse, membranous septa that divide it into a number of 

 vertically seriated air-cells. Walls of the frond composed of several rows of cells, 

 arranged in longitudinal series, and diminishing in size from the central tube out- 

 wards. Externally the surface is marked at short intervals by nodose swellings, 

 which are clothed with a whorl of numerous confervoid repeatedly pinnate articu- 

 lated filaments. Spores formed from the cells of moniliform, podlike filaments 

 borne along the inner faces of the lower divisions of the whorled filaments, oblate- 

 spheroidal, minute. 



A genus consisting of but one species, a native also of the shores of Europe, 

 where it is found from Italy to Scotland, generally in deep water. It is a slender, 

 filiform, distantly branched plant, delicately beautiful when its branches are young, 

 and the pencils of filaments that Avhorl them uninjured. 



1. Aetheocladia villosa, Duty. J. Ag. Sp. Alg., vol. 1, p. 162. Kiitz. Sp. 

 Alg., p. 573 (A. septenirionalis and A. azistralis, Kg.) Harv. Phyc. Brit. t. 64. 

 Conferva, villosa, Huds.—E. Bot. t. 546. I>iUw. Conf. t. 37- (Plate IV. A.) 



Hab. On submarine substances, in five (or more?) fathoms ; very rare. Cast 

 ashore at Smithville, near Wilmington, N. G., Mr. Charles Congdon. (v. v.) 



Boot a small disc. Fronds generally tufted, from six inches to nearly three feet 

 in length, very slender, once, twice, or thrice pinnated, filiform ; the pinna3 distant, 

 opposite, or rarely alternate, patent, simple or again pinnulated with similar, simple 

 pinnules ; all the divisions furnished at intervals of from half a line to a line, with 

 minute knoblike swellings which produce whorls of very delicate, byssoid, repeat- 

 edly pinnate jointed filaments of a pale green colour. The frond is traversed by a 

 wide tube, divided by transverse membranes at short intervals into joints or 

 chambers, four or five of which intervene between every whorl of filaments. 

 This tube is surrounded by several series of cylindrical cells, placed end to end 



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