Falklands, ete.] CRYPTOGAMIA ANTARCTICA. 197 
LVI. DIATOMACEJE, ۰ 
e ang. 
me The Waters and the Ice of the South Polar Ocean were alike found to abound with microscopic vegetables 
solitaris belonging to this Order. Though much too small to be discernible by the naked eye, they occurred in such 
M) Ñ countless myriads, as to stain the Berg and the Patk-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. Tn the open ocean, northward of the Frozen Zone, this Order, though no doubt almost universally present, 
pilde | generally eludes the search of the naturalist; except when its species are congregated amongst that mucous scum 
dmm — 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 Algæ are examined. To the south, however, of the belt of ice 
Rey, M.J, | which encircles the globe, between the parallels of 50° and 70° S., and in the waters comprised between that belt 
ited and the highest latitude ever attained by man, this vegetation is very conspicuous, from the contrast between 
a dift | its colour and the white snow and ice in which it is imbedded. Insomuch, that, in the eightieth degree, all 
"da ^| the surface-ice carried along by the currents, the sides of every berg, and the base of the great Victoria Barrier 
dem, ad 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 
ded Alge are in carbonate of lime), it is obvious that the death and decomposition of such multitudes must form 
sedimentary deposits, proportionate in their 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 
Exe | 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 Diatomacee. These, on being put into water, rendered it cloudy, like milk, and took many hours to sub- 
y, Di 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 
undant on organic compounds of the bottom frequently bore but a small proportion to the inorganie. 
Being indebted to the works of the illustrious Ehrenberg for all I knew of these organisms, previous to the 
pos whe sailing of the Antarctic Expedition, I had supposed the Diatomacee to belong to the Animal Kingdom *; and as 
"IT EN they are unaccompanied in the Antarctic region by any evidence of a higher order of plants, I had always supposed 
yi = 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 
sus ng, other eminent Cryptogamic botanists. ۲ 
js ds * It is well known that the true nature of the Diatomacee 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 Diatomacee conjugating, in a manner perfectly analogous to that 
pursued by the Zygnemata : 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 Zunotia, 
and Gomphonema, illustrating this important discovery, and mounted in fluid, after the beautiful plan invented by 
that gentleman for preserving vegetable tissues moist, and always ready for the microscope in the form of slides. 
