Page:The Botany of the Antarctic Voyage.djvu/540

504 I must offer some apology for omitting a class of organisms which have been investigated, and considered of vegetable origin, by Prof. Ehrenberg, and which are almost equally abundant in the Antarctic Ocean with the Diatomacea, whether on the surface or at the bottom of the sea: these are the Phytolitharia, Ehrb. I am not aware of the precise limits of this Order, and of many of the genera composing it; but from casual allusions, I gather that the term Phytolitharia is a conventional one, employed to designate the siliceous and other inorganic particles, deposited in plants of a higher structure. Thus, Lithodermatium is a genus whose species are represented by modifications of the siliceous epidermis of one or many species of JBquisetum; and the Lithostylidia are the siliceous cells of Graminea. It is not my object to discuss in this place the expediency of constituting such orders, genera, and species. The total absence of Equiseta from the Antarctic Flora, and of Graminem or other phsenogamic plants from any position within 700 miles of Victoria Barrier where the Phytolitharia abound, renders it in the highest degree improbable that the latter should be of vegetable origin,

A few remarks on the phases and situations under which these curious vegetables occurred, will not be misplaced here, especially as I have little to add to what is already known of their habits and organization.

Scattered on the surface of the ocean, the Antarctic Diatomaceæ were seen connected in filaments, or resolved into the simple frustules, of which they are composed. When entire, they shewed no signs of motion or irritability. The grumous or granular contents of the cells were yellow under the microscope; but in mass the same species assumed an orange-brown, or burnt Sienna colour; the intensity of which depended on the denseness with which they were packed together.

The various means employed for selecting the species varied according to circumstances, as the following enumeration of the processes pursued will show. 1. Sea-water was filtered through closely woven bibulous paper (filter-paper), which latter was folded, dried, and carefully put away. If a certain measure of water be always thus treated, an approximate knowledge of the abundance and scarcity of the various species and genera occurring at different positions, may be gained. 2. The scum of the ocean almost invariably contains many species entangled in its mass ; it was preserved in small phials, well secured. 3. A tow-net of fine muslin, used when the vessel's rate does not exceed two or three knots, secures many kinds, which may be washed off the muslin, and collected on filter paper. 4. The stomachs of Salpæ and other (especially of the naked) mollusca, invariably contain Diatomaceæ, sometimes several species. These Salpæ were washed up in masses on the Pack ice, and in decay they left the snow covered with animal matter impregnated, as it were, with Diatomacea: the reliunia were preserved in spirits. 5. The dirt and soil of the Penguin Rookeries, and especially their Guano, abound in Diatomaceæ the contrary, I cannot but suspect that some of these Phytolitharia are the remains of Crustacea, and especially the siliceous (?) particles, which occur in the tunics of naked Mollusca., perhaps originally swallowed by the Salpæ and Cuttle-fish, which themselves become the prey of the Penguins. 6. Ice encloses Diatomaceæ: they are deposited on the already formed ice by the waves, or frozen into its substance during calm weather, when the upper stratum of water rapidly congeals. Ice, so formed, generally breaks up by the swell of the sea into thin angular masses, which become orbicular by attrition, whence the name Pancake-ice. The Pancake-ice was often seen a few hours after a calm, covering leagues of ocean, and uniformly stained brown from the abundance of these plants. It was taken in buckets, and when removed from the water appeared perfectly pure and colourless. On melting, however, it deposited a pale red cloudy precipitate, excessively light, consisting wholly of Diatomaceæ. This precipitate was bottled on the spot, and proved