“Reverting to the Oolitic plants, I have again and with better success been experimenting upon the thin transparent films of leaves, chiefly of _Taeniopteris vittata_ and _Cyclopteris_, which from their tenuity offer fine objects for the microscope.... By many delicate trials I have ascertained the existence still in these leaves of resin and of tannin.... I am seeking among the filmy leaves of the _Fucoides_ of A. Brongniart for iodine, but hitherto without success, and indeed can hardly expect it, as probably did iodine exist in them, it must have long ago entered into new combinations[124].” Apart from this difficulty, it is not surprising that Dr Murray’s search for iodine was unsuccessful, considering how little algal nature most of the so-called Fucoids possess. Some of the most perfectly preserved tissues as regards the details of cell contents are those of gymnospermous seeds from Autun. In sections of one of these seeds which I recently had the opportunity of examining in Prof. Bertrand’s collection, the parenchymatous cells contained very distinct nuclei and protoplasmic contents. In one portion of the tissue in the nucellus of _Sphaerospermum_ the cell walls had disappeared, but the nuclei remained in a remarkable state of preservation. The cells shown in fig. 42 are from the ground tissue of a petiole of _Cycadeoidea gigantea_ Sew.[125], a magnificent Cycadean stem from Portland recently added to the British Museum collection; in the cell _A_, 1, the nucleus is fairly distinct and in 2 and 4 the contracted cell-contents is clearly seen. Other interesting examples of fossil nuclei are seen in a _Lyginodendron_ leaf figured by Williamson and Scott in a recent Memoir on that genus[126]. Each mesophyll cell contains a single dark nucleus. The mineralisation of the most delicate tissues and the preservation of the various forms of cell-contents are now generally admitted by those at all conversant with the possibilities of plant petrifaction. If we consider what these facts mean—the microscopic investigation of not only the finest framework but even the very life-substance of Palaeozoic plants—we feel that the aeons since the days when these plants lived have been well-nigh obliterated.