Abstract
IN a recent essay by Prof. Adolf Weiss, of Lemburg (“Zum Baue und der Natur der Diatomaceen”), it appears to be demonstrated that the siliceous investment of these little plants has cellulose to its base. The silex is infiltrated to a variable extent in the different families, and the mode of its deposition can to a certain extent be ascertained by examination with polarised light. In opposition to the opinion hitherto generally admitted, Prof. Weiss shows that the siliceous coal is capable of polarising light; and he has found also that it contains a certain amount of iron-oxide compounds, which are for the most part in an insoluble condition. He strongly objects to the view that the Diatomaceæ are one-celled organisms, but contends that each frustule is composed of numerous very minute but perfectly individualised cells. The different markings on the frustules—areolæ, ribs, crests, &c.—are in no way caused by the contour lines of the several cells of which they are composed. The size of the cells is very variable. In Triceratium favus they are as large as 0.008 of a millimetre, whilst in Hyalosira delicatula they do not exceed 0.00025 of a millimetre. Each cell is arched, and, as a rule, prolonged into a papilliform process at its centre. The papilæ are the cause of the moniliform or pearl necklace-like markings of diatoms when examined with high powers, and which appear as striæ with low powers. The large cavity between the two frustules is, he thinks, comparable to the embryo-sac of higher plants; and Weiss has succeeded in observing the development of new individuals in it. The product of this new individual indicates the alternation of generations in the Diatomaceæ.
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Nature of Diatoms. Nature 6, 92–93 (1872). https://doi.org/10.1038/006092b0
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DOI: https://doi.org/10.1038/006092b0