66 
FUCACEiE. — Cystoseira. 
IY. 
Nearly related to the preceding genus, from which it differs in the air-vessels, 
which do not here run together into a compound vessel of many cells, though they 
form little chains, one inflation of the branches succeeding another but remaining 
separate. Upwards of twenty species are described, of which thirteen or fourteen 
are found in the Mediterranean, and four occur on the Atlantic shores of Europe 
as far north as Great Britain, reaching their highest latitude on the western coast 
of Ireland. The group is scarcely represented in the New World. One or two of 
the European species are stated, on doubtful authority, to occur on the shores 
of Guiana and Brazil, where probably something else has been mistaken for 
them ; but there is no record of any having been detected on the eastern shores of 
America, where European forms might, more naturally, have been anticipated. 
The only North American species with which I am acquainted is the following 
from California. 
1 . Cystoseira expansa , Ag. ; frond (its base unknown) very long, filiform, 
slender, smooth, repeatedly pinnate, distichous, the ultimate ramuli simple or 
forked ; air-vessels ellipsoidal, chained, several together in the lower half of the 
penultimate and ultimate branchlets ; receptacles “ cylindrical, warted, paniculate, 
subconfluent with the tops of the branches.” J. Ag. Sp. Alg.,vol. 1, p. 226. Cystoseira 
Douglasii, Haw. in Bot. Beecliey , p. 407. Sirophysalis Douglasii , and S. expansa, 
Kiitz. Sp. Alg ., p, 603. (Tab. I. B.) 
ITab. Probably in deep water. At Monterey, California, Mr. Douglas ; Dr. 
Coulter, (v. s. in Herb. T.C.D.J 
The root and lower part of the stem are unknown. Our specimens consist of 
portions of stems (or branches) from two to three feet in length, and about 
half a line in breadth, compressed, becoming narrower and more filiform toward 
the extremities ; and thrice or four times divided in an alternately pinnate 
manner. The ultimate ramuli show a disposition to become dichotomous. Air- 
vessels from one to two lines long, ellipsoidal, in strings of four to eight, forming 
swellings in the smaller branches and ramuli ; the string of swellings generally 
commencing near the base of the ramulus, and extending at least through its lower 
Half. In the ultimate and smaller divisions the inflations are proportionally fewer 
and are sometimes solitary. I have not seen the receptacles which J. Agardh 
describes as being “ 6 — 8 lines long, everywhere of equal thickness, warted, and 
nearly all pedicellate.” 
This is probably a species of very great length, the portions of branches which 
are alone known to us being evidently only the upper divisions. There is a 
striking resemblance in habit between these and the most branching forms of 
Halidrys osmundacea , but in the present species each vesicle stands perfectly apart 
from its neighbour, however closely they may approximate. 
