plane, and it often depends on the smoothness of the water how long they may remain so. This variety is abundant everywhere in the Antarctic seas.
Variety y. angustifrons. The character, drawn from the tenuity of the vesicles, is utterly unsatisfactory, being attributable to the drying of the specimen, and the locality of the live plant. Besides the Antarctic habitats of this variety, it has been found in Chili, New Zealand, and the Indian Ocean.
Varieties e. luxurians, and (. membranacea. If any form of this genus deserves specific distinction it is surely the noble one we have designated c. luxurious; and yet permanent characters, distinguishing it from pyrifera, were vainly sought in plants gathered on the shores of Berkeley Sound. Both there and at Cape Horn these two states inhabited deep and still waters, where, as might be expected, the Macrocystis would acquire its greatest development, where its substance would be most membranous, its stems most slender, and the vesicles broad with thin walls, and the base of the frond broadest. We have seen no specimens of these varieties except what were brought home by the Antarctic Expedition.
Variety rj. HumbolcUii, at first sight appears different, and the specimens found on the outer shores of the Ealklands we once thought might belong to a distinct species. The rounded form of the vesicles, however, which affords the main character, is not constant on specimens collected in the Coral Islands by Captain Beechey. It has been gathered at various places along the west coast of South America, from Cape Horn to the Equator, and far westward in the Pacific amongst the Coral Islands.
With regard to other states, which we have not seen, the most remarkable is the M. Orbignyana of Montagne (Sert. Patagon. p. 12. t. 1.), which has the vesicles remarkably lengthened and the leaf attenuated at the base above the vesicle into a distinct petiole. The M. latifolia, Bory, is intermediate between our <•. luxuriant and pyrifera. M. tenuifolia, Post, and Ruppr., is apparently between M. pyrifera and M. zostertzfolia. The character of M. planicaulis is founded on the compression of the stem, produced by drying, and we have therefore quoted it as a synonym.
In thus bringing together under one, the ten species which have been described by five authors, of whom hardly one has ever seen even the genus in a living state, we are only taking advantage of opportunities which a long residence in the Southern Hemisphere has afforded. Without studying these plants on the coasts they inhabit, it is impossible to judge of the influence of local causes on their plastic forms. We venture to say that few botanists in Europe have seen even tolerable specimens from one single plant of this Alga, such, we mean, as give a fair idea of the differences between the leaves and bladders, along, perhaps, 300 feet of stem, with the submerged fructifying fronds from the root. Out of some thirty specimens brought home by ten different collectors and preserved in the Hookerian Herbarium previous to our visit to the seas which M. pyrifera inhabits, not one conveys any notion of the variations which even a sohtary individual can assume.
The fructification of this plant appears to be produced only on the young newly-formed submerged leaves, where it forms large irregular brown patches or sori, causing the frond to separate into two lamina;, as in Lessonia. The spores are fusiform, first divided into four, each afterwards breaking up into as many sporidia. Under a high power the surface of the fertile frond is seen generally to be covered with anastomosing raised lines of a dark colour, on which the spores are placed; the spaces between are pale and transparent. We have not noticed spores, like what are figured by Agardh (1. c. t. 28. f. 11), but plenty of the kind he represents at f. 10 6 of the same plate, though not contained in sporangia. These, magnified as highly as his f. 10 6 , are evidently divided, as in D'Urvillaa. The granules also, which occur abundantly with the spores, are surrounded by a hyaline border, and divided into two to four sporidia ; we suppose them to be merely small spores.
It is seldom that the history of an Alga is likely to afford interest or amusement to the general reader, unless it be a positively valuable plant in an economic point of view. Like the Sargasso-weed of the Tropics, however, the Macrocystis is so conspicuous, and from its wandering habits, often occurs so unexpectedly, that the attention of our earliest voyagers has been directed to it, and we are consequently led back by our enquiries into its first
