IV. 
SPOROCHNACEiE, — Arthrocladia. 
75 
Synopsis of the North American Genera. 
I. Artiirocladia. Frond pinnate, filiform, noclose, hollo av ; the tube articulated 
within. Nodes whorled Avith delicate filaments. 
II. Desmarestia. Frond pinnate, either filiform, compressed, or flat, solid. 
III. Chnoospora. Frond dichotomous, flat. 
I. ARTHROCLADIA, Duly. 
Frond cylindrical, pinnated, traversed by a wide, empty tube Avhich 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 roAvs of cells, 
arranged in longitudinal series, and diminishing in size from the central tube out- 
Avarcls. Externally the surface is marked at short intervals by nodose swellings, 
which are clothed Avith a whorl of numerous confervoicl repeatedly pinnate articu- 
lated filaments. Spores formed from the cells of moniliform, podlike filaments 
borne along the inner faces of the loAver divisions of the whorled filaments, oblate- 
spheroidal, minute. 
A genus consisting of but one species, a native also of the shores of Europe, 
Avliere it is found from Italy to Scotland, generally in deep water. It is a slender, 
filiform, distantly branched plant, delicately beautiful Avhen its branches are young, 
and the pencils of filaments that whorl them uninjured. 
1 . Arthrocladia villosa , Duby. J. Ay. Sp. Alg ., vol. 1 , p. 162. Kiitz. Sp. 
Alg., p. 573 (A. septentrionalis and A. australis , Kg.) llarv. Bhyc. Brit. t. 64. 
Conferva villosa , FLuds. — E. Bot. t. 546. Dillw. Conf. t. 37. (Plate IY. A.) 
Hab. On submarine substances, in five (or more?) fathoms ; very rare. Cast 
ashore at Smithville, near Wilmington, N. C., Mr. Charles Congdon. (v. v.) 
Root a small disc. Fronds generally tufted, from six inches to nearly three feet 
in length, very slender, once, tAvice, or thrice pinnated, filiform ; the pinnae 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 Avhich intervene between every Avhorl of filaments. 
This tube is surrounded by several series of cylindrical cells, placed end to end 
