Falklands, etc.] FLORA ANTARCTICA, 503 



LVI. DIATOMACE^, Ag. 



The Waters and the Ice of the South Polar Ocean were alike found to abound with microscopic vegetables 

 belonging to this Order. Though much too small to be discernible by the naked eye, they occurred in such 

 countless myriads, as to staiu the Berg and the Pack-ice, wherever they were washed by the swell of the sea ; and 

 when enclosed in the congealing surface of the water, they imparted to the Brash and Pancake-Ice a pale ochreous 

 colour. In the open ocean, northward of the Frozen Zone, this Order, though no doubt almost universally present, 

 generally eludes the search of the naturalist ; except when its species are congregated amongst that mucous scum 

 which is sometimes seen floating on the waves, and of whose real nature we are ignorant ; or when the coloured 

 contents of the marine animals who feed on these Algae are examined. To the south, however, of the belt of ice 

 which encircles the globe, between the parallels of 50° and 70° S., and in the waters comprised between that belt 

 and the highest latitude ever attained by man, this vegetation is very conspicuous, from the contrast between 

 its colour and the white snow and ice in which it is imbedded. Insomuch, that, in the eightieth degree, all 

 the surface-ice carried along by the currents, the sides of every berg, and the base of the great Victoria Barrier 

 itself, within reach of the swells, were tinged brown, as if the Polar waters were charged with oxide of iron. 



As the majority of these plants consist of very simple vegetable cells, enclosed in indestructible silex (as other 

 Alym are in carbonate of lime), it is obvious that the death and decomposition of such multitudes must form 

 sedimentary deposits, proportionate in then - extent to the length and exposure of the coast against which they are 

 washed, in thickness to the power of such agents as the winds, currents and sea, which sweep them more energetically 

 to certain positions, and in purity to the depth of the water and nature of the bottom. Hence we detected their 

 remains along every ice-bound shore, in the depths of the adjacent ocean, between eighty and 400 fathoms. Off 

 Victoria Barrier (a perpendicular wall of ice, between one and two hundred feet above the level of the sea), the 

 bottom of the ocean was covered with a stratum of pure white or green mud, composed principally of the siliceous 

 cells of Diatomacece. These, on being put into water, rendered it cloudy, bke milk, and took many hours to sub- 

 side. In the very deep water off Victoria and Graham's Land, this mud was particularly pure and fine ; but 

 towards the shallower shores, there existed a greater or less admixture of disintegrated rocks and sand ; so that the 

 organic compounds of the bottom frequently bore but a small proportion to the inorganic. 



Being indebted to the works of the illustrious Elrrenberg for all I knew of these organisms, previous to the 

 sailing of the Antarctic Expedition, I had supposed the Diatomacece to belong to the Animal Kingdom *; and as 

 they are unaccompanied in the Antarctic region by any evidence of a higher order of plants, I had always supposed 

 vegetation to cease at a much lower latitude than these productions actually attain. The species were, however, 

 collected on every available occasion, and transmitted, on my return to England, to Professor Ehrenberg, whose 

 determination of the genera and species is here introduced, at the suggestion of the Rev. M. J. Berkeley and 

 other eminent Cryptogamic botanists. 



* It is well known that the true nature of the Diatomacece has been long and unsuccessfully disputed, being 

 claimed both by botanists and zoologists. No conclusive evidence on this subject had been adduced, till, within these 

 very few days, it was the singular good fortune of my friend, Mr. Thwaites, of Bristol, a most acute observer and 

 profound Cryptogamist, to detect several species of Diatomacece conjugating, in a manner perfectly analogous to that 

 pursued by the Zygneiaata : a fact which leaves no doubt of their vegetable origin in the minds of persons acquainted 

 with his interesting observations. I am indebted to Mr. Thwaites for specimens of three British species of Eunotia, 

 and Gomphotwma, illustrating this important discovery, and mounted in fluid, after the beautifid plan invented by 

 that gentleman for preserving vegetable tissues moist, and always ready for the microscope in the form of slides. 



