30. IRID.EA, Bory.
1. Irid^a Radida, Bory; Fl. Antarct. Pt. 1. p. 188.
Hab. Hermite Island, Cape Horn ; Falkland Islands and Kerguelen's Land, very abundant. Cockburn Island ; at the limits of southern vegetation, on the beach, rare and bleached.
So abundant are the Iridea in the South Polar Oceau, and so variable in their form and texture, that we can scarcely hope to arrive at any accurate knowledge of the species until they shall have been studied in a living state; and then it is not improbable that the genus will be considerably reduced; and one or two of the more common species be found to assume forms as dissimilar as those of our Laurencia pinnatifida.
There exist in the Hookerian Herbarium, authentic specimens of the Fucus bracteatus of Gmelin, as figured in Turner's ' Historia,' collected both at the Cape of Good Hope and in North West America, by Mr. Menzies. These are (as is generally the case with the specimens of the larger Fuci, preserved in our Herbaria) smaller and of that lanceolate form which other Iridea present in a young state. Then texture is very thick, densely cartilaginous, opaque ; and covered with tubercles which fall away, leaving a cribriform frond both when immature and older. This great density is a very remarkable character,- and observable in the plant here referred to that species, which, when full grown, becomes broadly ovate, or orbicular, and cordate or rounded, or narrowed at the base ; with the lamina more or less and variously divided, sometimes three feet broad, or upwards. The largest specimens we have never seen attached, though they are abundant, washed up on the beach, and probably attain then-great size on the outer rocks.
Since the publication of the first part of this work, we have, through Dr. Montagne's kindness, had the opportunity of inspecting the I. laminarioides, Bory, of Lord Auckland's Group : specimens of which are in our Herbarium from the same island ; but which we had previously regarded as a more debcate state of /. Radida. Even what we consider the true /. Radida of Lord Auckland's Group and Kerguelen's Land, is not so dense in the frond as the specimens of the Falkland Islands and Cape of Good Hope are. Both this and the following species have the surface frequently covered with granules, tubercles or pedicellate pear-shaped organs ; or in the young state with elongated fleshy bodies similar to those of the /. stiriata, Bory. The /. stiriata, according to the descriptions, may belong to a state of this, or the following, or many other forms of the genus : it is, however, a narrower, smaller species, with a much more dense frond than even /. Radida.
2. Ieid/ea cordata, Bory, in Bnperrey Toy. Bot. p. 104 ; et I. roicans, p. 110. 1. 13 et 13 lis. Halymenia cordata, Agardh, Sp. Alg. p. 201. Fucus cordatus, Turner Hist. Fae. t. 116.
Var. /3. ciliolata ; stipite brevi cartilagineo cuneato ciliato-dentato mox in frondem simplicem ovato-lanceolatam desinente, fronde latisshna basi cuneata v. cordata apice obtusa v. acuta v. emarginato-bifida membranacea rubra plana nitente lsevi margine vix undulata. Nobis in Lond. Journ. Bot. vol. iv. p. 263.
Var. y. dlchotoma ; stipite brevi mox cuneato furcato v. pluries dichotomo sensim in frondem late cuneatam obovatamve desinente, segmentis integris vel divisis margine dentatis lobatis proliferisve.
Hab. Hermite Island, Cape Horn, and the Falkland Islands ; both varieties very abundant.
This species, when fresh, well deserves the brilliant description of its beautiful tints, given by M. Bory on the authority of Admiral D'Urville and M. Gaudichaud. It is one of the most common Alga of the southern extremity of America and the Falklands. In its younger state, the fronds are obovate or spathulate, like those of /. laminarioides, figured by Bory, and soon expand into lamiuee, variously modified, according to situation and exposure, with relation to the force of the sea, the nature of the bottom, the currents, depth, and protection afforded by other Alga ; for no two fronds of a similar shape are usually to be found within a few yards. Indeed,
