Falklands, etc.] CRYPTOGAMIA ANTARCTICA. 151 
except by one of its own aspect; for its nearest and, indeed, very near ally, is a native of New Holland; whilst in 
size, luxuriance and beauty of growth, the present surpasses not only all other species of the genus, but almost the 
whole of the group Cystoseiree. 
We are accustomed to regard the ocean as so ever-active and powerful an agent in facilitating migration, and 
its uniform temperature is so conducive to the general diffusion of species, that it seems almost wonderful that ۸ 
should have limits to their distribution, especially in waters which gird the globe on the same parallel of latitude, 
and whose unchecked swells and currents literally extend over every degree of longitude. The remarkable increase in 
-temperature of the tropical over the polar seas of the Atlantic may, and probably alone does, check the progress of 
the Macrocystis in its course from Cape Horn to the Equator in that ocean, for, as I shall afterwards show, the same 
sea-weed can float with the colder currents of the Pacific from the same Cape to Behring’s Straits; but no such 
obstacle prevents the fullest interchange of Cystoseiree between New Zealand and the temperate seas of South 
America. It, however, is the fact, that whilst this group literally abounds in certain latitudes and longitudes, 
which are those of New Holland and the West Pacific, they are nearly absent from analogous positions in the 
longitude of South America. 
Throughout all latitudes the two tribes Fucoidee and Cystoseiree form that prevailing marine vegetation to which 
the name sea-weed is commonly applied ; and the different genera so far arrange themselves within geographical limits 
as to present, with such few exceptions as the Seytothalia Jacquinotii, a most harmonious assemblage. Thus, 
in the opposite colder and frigid zones the waters are inhabited by certain genera of Fucoidee which are in a great 
measure representatives of one another; as, in 
O ی نی‎ l Fucus proper, and } are represented in analogous } D'Urvillea, and 
Himanthalia, southern zones, by Sarcophycus, Kütz, 
None of these genera approach the tropics, for the Fucoidee abound towards the poles, and there attain their greatest 
bulk, diminishing rapidly towards the Equator, and ceasing some degrees from the Line itself. The representatives 
of the Cystoseiree in the higher latitudes of the opposite hemisphere, are equally appropriate with those of 
Fucoidee, for we have in 
Cystoseira, and ] represented in the ) Blossevillea, and 
the north cool zone Halidrys, south cool zone, by Seytothalia ; 
whilst the immense genus Sargassum finds its maximum in lower latitudes, and under the Equator itself. 
Such are the salient features of the distribution of these tribes, which are not influenced by the minor divisions, 
chiefly local assemblages of small genera, affecting exclusively certain coasts or bays. 
3. LESSONIA, Bory. 
1. Lessonia fuscescens, Bory, in Duperrey Voy. Bot. Crypt. p. 15. t.2. f. 2. ett.3. Post. et Ruppr. 
Illust. Alg. p. 9. t.3 et p.4. t.39. f. 14-18.  L. flavicans, D'Urville, in Mém. Soc. Linn. Paris, vol. iv. 
p.594. (Tas. CLXVIL, CLXVIIIT. 4., and Tas. CLXXI. D.) 
Has. Hermite Island, Cape Horn, and Falkland Islands; most abundant, always far beyond low-water 
mark. Christmas Harbour, Kerguelen's Land ; rare 
The fructification of the species of Zessonia occurs, as in Macrocystis, upon the surface of the fronds, and 
there forms large patches. In the present species the sori are situated beyond the middle of the leaf, they 
are oblong and nearly as broad as the lamina, of which they carry away the upper part when decaying, causing 
their broad apices to be two-horned. In none of our specimens is the point perfect, all the spores we have seen 
being situated on the edges of the sorus, which has itself fallen away from the frond. The air-cells are less 
numerous, and the spores are smaller, shorter, more densely packed than in the following species, and covered 
R 
